Graduation internship Dennis Hermus Utility power supply ...

Graduation internship Dennis Hermus

Utility power supply for offshore wind farm substations

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Date: 8/6/2011

Foreword

In the last year of the study Electrical Engineering at the Avans University of Professional Education in Breda a

graduation internship is needed to prove the requirements of an Electrical Engineer. Because I have also studied

Offshore Engineering & Automation at Avans University of Professional Education in Den Bosch I searched for

an company in the offshore industry. This resulted in HFG Engineering. HFG Engineering is a part of the

Heerema Fabrication Group(HFG) which is specialized in the engineering and fabricating of jackets, topsides

and structurals for the oil, gas and wind industry. HFG has facilities to design and build large constructions in

controlled conditions around the North Sea.

The main part of this report is a transformer substation platform for offshore wind farms in the North Sea. This

substation increases the generated voltage of the wind turbines. In this report I investigated in detail the utility

power supply part, which take care of the electrical power of components in different situations, and makes a

guide for the engineering of such a transformer substation. This utility power supply was a subject of many

discussions, problems and adjustments during engineering and building of previous projects. The structure,

welding, testing, ground investigations and the size and pricing of components are not treated in this report.

Because HFG Engineering is an international company this report is written in English.

By this way I would like to thank everyone who has made my graduation internship a success. This are

especially the company mentors of HFG Engineering Mr. Van der Heijden & Mr. Tillema, all the employees of

HFG Engineering and my mentor of Avans University of Professional Education Mr. Voermans.

Zwijndrecht, June 2011

Dennis Hermus


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Date: 8/6/2011

Contents

Foreword ........................................................................................................................................................................... 2

Summary ........................................................................................................................................................................... 4

1. Introduction .................................................................................................................................................................. 5

1.1 The company .......................................................................................................................................................... 5

1.2 Description of the problem ..................................................................................................................................... 5

1.3 Structure of report ................................................................................................................................................... 5

1.4 The origin and the future of offshore wind energy ................................................................................................. 6

2. Standards and guidelines .............................................................................................................................................. 8

2.1 Standards performing company .............................................................................................................................. 9

2.2 Standards Substation ............................................................................................................................................. 10

2.2.1 General Standards (design, implementation, operation) ................................................................................ 10

2.2.2 Electrical installation ..................................................................................................................................... 11

3. Reducing energy losses during transport by increase voltage. .................................................................................... 12

4. The installation of an offshore transformer substation platform ................................................................................. 13

4.1 The transformer substation ................................................................................................................................... 13

4.2 Electrical components of the utility power supply ................................................................................................ 14

4.2.1. High power components ............................................................................................................................... 16

4.2.2. Control and uninterruptible power supply .................................................................................................... 21

4.3 Worst-case scenario’s ....................................................................................................................................... 25

Conclusion ...................................................................................................................................................................... 28

Recommendation ............................................................................................................................................................ 29

List of used parameters ................................................................................................................................................... 30

Glossary .......................................................................................................................................................................... 31

References ...................................................................................................................................................................... 33

Annex 1: Project Management Document(in Dutch) ...................................................................................................... 34

Annex 2: standards ......................................................................................................................................................... 42

Detailed standards ...................................................................................................................................................... 42

Less important electrical standards ............................................................................................................................. 45

Annex 3: Reducing losses by using High Voltage Direct Current(HVDC) .................................................................... 46


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Summary

In the last year of the study Electrical Engineering at the Avans University of Professional Education in Breda a

graduation internship is needed to prove the requirements of an graduated Electrical Engineer. This graduation

internship is completed at HFG Engineering, which is specialized in the engineering of jackets, topsides and

structures for the offshore oil, gas and wind industry. In this report the utility power supply part of a transformer

substation for offshore wind farms is investigated in detail and a guide for the engineering of such a transformer

substation is made. The construction, calculation and redundancy of components of the utility power supply,

which takes care of the electrical power of components in different situations, were subjects of many

discussions, problems and adjustments during engineering and building of previous substation projects. This

report functions as a guideline for these discussions, problems and adjustments.

Before the utility power supply will investigated and recommended a few studies are done. The conclusions of

these studies are:

increasing the voltage will reduce losses. The cable losses(=resistance) will increase quadratically by

doubling the current. This resistance depends on many factors, like temperature and isolation, but that

influence is limited.

an enumeration of the legislation of an offshore substation is known. There are several standards for the

company, general standards for offshore substations and guidelines for the electrical installation which

are very important. The most important electrical standards describes the requirements of the whole

substation installation.

The advantages and disadvantages of HVDC compared to HVAC and the break-even point of costs for

AC and DC transmission, when varying the length of the connection, are known. HVDC will be

cheaper compared to HVAC after 90km between the substations.

The components of such a transformer substation could be chosen after these studies. The choice of these

components depends of many factors, such as performance, quantity and redundancy. The choice of redundancy

depends of several (quantity) analyses: HAZID, HAZOP and EMTP. The recommended structure of the offshore

transformer substation is made with using these analyses, conclusions and legislations.

This guide for the utility power supply part of a transformer substation for offshore wind farms will result to:

a good explanation to determine the various voltage levels.

an explanation, calculation and determination of the power of the different components.

which influences on components take into account.

different own power supply opportunities, like auxiliary generator, emergency generator and UPS, are

known and could be calculated.

the various worst-case scenarios, which a substation has to deal with, are known and a scenario could be

determined.

different outside power supply opportunities, like power taken from grid and power taken from wind

turbines, are known and could be determined.

The recommendation is to investigate a clean own power supply, the competitive advantage of the recommended

structure, the utility power supply of a convertor substation and other properties of components of different

fabricators.


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1. Introduction It is good to know something about the company HFG Engineering, the definition of the problem, why HFG

Engineering think it is important to solve this problem and why offshore wind is an important industry for the

future and for The Heerema Group.

1.1 The company

The Heerema Group is an international company and employ more than 2,000 people around the world. The

Heerema Group exists of Heerema Fabrication Group(HFG) and Heerema Marine Contractors(HMC). HFG is

specialized in the engineering and fabrication of jackets, topsides and structures for the offshore oil, gas and

wind industry. HMC transports, installs and removes all types of offshore facilities. These include fixed

structures, complex infrastructures and floating facilities, in shallow water, deep water and ultra-deep water.

Heerema Fabrication Group has facilities to design and build large constructions in controlled conditions. They

have three large production facilities situated around the North Sea, a workshop facility in Poland and the world-

wide operating multi-disciplined engineering company HFG Engineering in the Netherlands. HFG engineering

provide the engineering of the jackets, topsides and structures but also FEED studies, detailed design,

procurement support and engineering project management. HFG Engineering Europe was established in 2009 to

mainly serve the European and Scandinavian market and today has approximately 30 engineers, designers and

project managers.

1.2 Description of the problem

The main part of this report is a transformer substation platform for offshore wind farms in the North Sea. In this

report I investigated in detail the utility power supply part and made a guide for the engineering of such a

transformer substation. The utility power supply, which takes care of the electrical power of components in

different situations, was a subject of many discussions, problems and adjustments during engineering and

building of previous substation projects. With using this report it is possible for HFG Engineering to solve these

problems at the beginning of a project.

1.3 Structure of report

After this section you will find an introduction and explanation about the newest source of sustainable energy:

the grown wind industry. The following chapter will treat the standards for engineering and building of offshore

substations. To keep this report readable the most referenced standards for engineering and building are

summarized in the annex and the most technical expressions are explained in the glossary. After the explanations

about standards and laws the technical part of this report will follow.

In chapter 3 you will find the explanation about the purpose of an offshore transformer substation and the

explanation of increasing voltage. The last chapter will treat the intern components and the recommended

structure of the transformer substation. The jacket, welding, testing, ground investigations, thermography and the

size, choice and pricing of components are not treated in this report.

Because The Heerema Group, and so HFG Engineering, is an international company this whole report is written

in English.


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1.4 The origin and the future of offshore wind energy

Today, green or sustainable energy is a hot item in the news, because today’s way of generating energy has a

negative impact on the environment. Our energy will be more expensive in the future if we keep using fossil

fuels. There are a lot of different ways of generating sustainable energy, but wind is the most popular one

because wind is everywhere. The development of wind energy has started on land but nowadays offshore wind

farms are increasing because the wind on the sea blows stronger and the yield is higher here. In the past offshore

wind energy was impossible but it is slowly becoming reality. An offshore wind farm is usually situated a few

miles from the shoreline, in order to prevent so-called visual pollution and because the wind is more constant

here. Offshore wind contains a higher capacity factor (35% to 40%) than onshore wind (23% to 28%) so the

efficiency is greater. Because power is proportional to the cube of the speed, this amounts to an offshore wind

yield of about 60% more revenue compared to onshore wind.

The choice of placing a wind farm depends on many factors, like ports and branches of the high voltage network

(grid). The government looks at these factors and decides the location of an offshore wind farm. For example, in

the Netherlands it is not desirable to place a wind farm within the 12 miles zone and the ports of Rotterdam and

Antwerp should be taken into account. The fact that only a branch of the high voltage network is in Beverwijk,

the Maasvlakte and Eemshaven gives only a few places to build. These problems are less in Germany and the

United Kingdom where the offshore wind industry increases faster. Once the location of the park is chosen, there

is calculated how the wind turbine generators should be placed and where a substation will be situated.

So far, Denmark, the Netherlands and the United Kingdom are leaders in offshore wind energy production

(February 2011) but in the next decade this will change significantly. Japan, Germany and the USA haves a lot

of future plans for offshore energy production. The largest wind farm is planned in Japan for 2025. This will

have to generate 250000MW, while the Netherlands has set a target of 6000MW for 2020. Also, the traditional

wind turbine will make way for new models. The traditional wind turbine has three blades, a horizontal shaft, a

gearbox and a generator in the nacelle, as shown in figure 1. There are now newer models being designed which

have a vertical axis, multiple blades, no gearbox or no old-fashioned ball bearings.

Figure 1: placing of a generator in a modern nacelle


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Especially Germany, USA and Japan are developing new models for offshore wind farm projects. Wind energy

projects are developed by energy companies and public assistance shall be covered. This development is also an

increasing demand for structural wind turbines and substations. Because the development of offshore wind

energy has only just begun, there are only a few specialized companies. The offshore wind turbines are mostly

land turbines and are suitable for offshore use after a little modification. But developments go quickly in this

industry. If the applications for the award of offshore wind farms continue to increase, industry will change and

will specialize it. However, it is launched by the government by providing subsidies.

The use and placement of offshore wind farms is thus highly dependent on many factors but it is for sure that

growing numbers around the world will be posted. We are now living in the sustainable era where wind turbine

generators are an important, if not the most important, part in sustainable power generation. However, this

industry is still at an early stage and must therefore be taken up by subsidies. The knowledge is there,

environment polluting energy is more taxed by most governments and there is enough space at sea so it is only a

matter of time before the offshore wind industry will not need subsidies anymore. The more installed capacity,

the less investment per kW, as shown in the expected trend of Figure 2.

Figure 2: the expected trend of installed capacity and investments of offshore windfarms (source: NWEA)


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2. Standards and guidelines

All industrial (offshore) projects are confronted with many laws and standards. There are rules concerning

construction, transport and electrical energy supply. There are laws to protect the environment and surroundings

and there are rules for designing and building a system and overall security. This legislation is not made to make

projects difficult and expensive but to be sure that projects are good, safe and clearly performed. But there is also

legislation to promote wind energy, because wind energy is important for the goals of climate and renewable

energy.

To ensure that projects are this good, safe and clear, there are many guidelines drafted by national institutes like

the NEN (Dutch Standards Institute) in the Netherlands, BSI (British Standards Institution) in Great Britain and

DIN (German Standards Institute) in Germany. The national guidelines of these institutes are seen by

international institutes such as the CEN (European Committee for Normalization) and ETSI (European

Telecommunications Standards Institute) but also by global institutes such as ISO (International Organization for

Standardization) and IEC (International Electro technical Commission). By comparing and summarizing these

national standards, they become international standards. This is done to get international clarification, because

many products and companies come from abroad or work there. These standards are also prepared in case of

accidents or uncertainties; it is possible to fall back on the person who is responsible for the mistake. Guidelines

are set to include quality management, design, documenting, performance, safety and use of materials. The

guidelines are written in such a way that they are all equal to each other but safety is still top priority. In this

chapter, the most important laws, rules and standards will be explained but only concerns the electro technical

parts of substations for offshore wind farms. Laws, rules and standards for offshore WTG are disregarded.


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2.1 Standards performing company

Because offshore is work at sea, safety has the highest priority. To be sure that safety is not compromised, a lot

of standards are made. These standards are discussed when a company signs a contract for a project; to be sure

that the customer and the company performing it are aware of both. Today, the customer also requires that the

company (and employers) own this certification. The international standards that are used usually contain

multiple national standards. If the international standard is met, the company also includes the knowledge of the

national standards. This chapter will only refer to the standards; the summarized version is given in annex 2.

ISO-EN 9001

ISO-EN 9001 is an international standard for quality. This standard is used not only in the offshore industry but

generally as a significant meaning for performance of quality companies. This standard contains requirements

which a company must meet so that it is capable to deliver quality. This standard does not mean that the

company or organization actually delivers quality, but it proves that it can deliver this quality. ISO9001 can be

used as a client to assess whether the company or organization shall be able to meet customer requirements, the

requirements of the company itself and the laws and regulations that have been made for that product. There are

more than 1 million issued certificates and most manufacturing companies have it in possession.

ISO-EN 3834

For offshore construction companies it is important that their products match good tensions and forces. By the

ISO9001 standard, the customer is more confident that a product meets all requirements, but ISO9001 does not

refer to the requirements for welding. In ISO9001 welding is described only as a special process. This is the

reason why customers of welding products are often demanding for the ISO3834 certification requirements. The

ISO3834 ensures that a company of welding operates on a clearly more advanced level and is regularly tested

through audits. Following the correct steps before, during and after production will obtain a product with the

right quality, ISO 3834 describes this.

ISO-EN 14001

ISO- EN14001 is an international standard which indicates the demands an environmental management must

meet. If an environmental management system is desired, it must be certified to this standard but with most

companies it will be a part of the daily management during the ISO9001 audits. This standard focuses on

controlling and improving environmental performance and environmental work at a company. Because this is

normally a standard part of ISO9001, it contains fewer assumptions.


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2.2 Standards Substation

Chapter 3 defines which electronic components and systems the substation platform contains. All these devices

will be tested based on standards before they can be placed in the substation. Because the substation is finally

placed at sea, processes very high voltages and run independent the standards for this energy conversion

facilities are more strict than the substations on land. The most important standards for engineering are given in

this paragraph; extensive parts and less important standards are given in annex 2.

2.2.1 General Standards (design, implementation, operation)

These standards are made for design, implementation and operation for offshore substations for wind farms.

These standards do not cover oil and gas installations, wind turbines, subsea cables, procedures for construction,

operation or decommissioning of the offshore substations and subsea installations.

DNV-OS-J201

It has been developed primarily to assist in the development of new offshore transformer substations, HVDC

substations and associated accommodation platforms. Locally applicable legislation may include requirements in

excess of the provisions in this standard depending on type, size, location and intended service of the installation.

Regional guidance is included throughout this standard by example only. The standard focuses on fixed, bottom-

mounted installations. It may also be applied to floating installations if additional requirements are being taken

into account. The principles, requirements and guidance shall be applied to all stages in the lifecycle of the

installation, beginning at the concept design stage. Updates shall be made throughout the detailed design phase.

The principles shall also be applied during the construction, operation and decommissioning phases and

whenever modifications are made.

BSH Standard Design of Offshore Wind Turbines

This standard is intended to provide legal and planning security for development, design, implementation,

operation and decommissioning of offshore wind farms within the Marine Facilities Ordinance. It is dynamic

and integrative, so that it will be possible to take account of new knowledge and developments. A range of

representatives from expert bodies and institutions have been involved in developing this standard, and have

played a constructive role in its development. The representatives of the classification societies Det Norske

Veritas (DNV) and Germanischer Lloyd (GL) provided expert accompaniment for the process. Representatives

of the business and scientific communities made valuable contributions, so that overall it has been possible to

create a solid basis for constructive cooperation in terms of system security in order to protect the marine

environment and maintain the safety and efficiency of navigation.

IEC EN 61400-3

This part of IEC 61400 specifies additional requirements for assessment of the external conditions at an offshore

wind turbine site and it specifies essential design requirements to ensure the engineering integrity of offshore

wind turbines. Its purpose is to provide an appropriate level of protection against damage from all hazards during

the planned lifetime. This standard focuses on the engineering integrity of the structural components of an

offshore wind turbine but is also concerned with subsystems such as control and protection mechanisms, internal

electrical systems and mechanical systems. A wind turbine shall be considered as an offshore wind turbine if the

support structure is subject to hydrodynamic loading. The design requirements specified in this standard are not

necessarily sufficient to ensure the engineering integrity of floating offshore wind turbines.


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2.2.2 Electrical installation

These standards are made for engineering of offshore electrical systems and installations for substations of wind

farms. The most complete important standards for electrical installation are given in this paragraph.

IEC 61892: Mobile and fixed offshore units - Electrical installations

The IEC 61892 series contains provisions for electrical installations in mobile and fixed offshore units including

pipeline, pumping or 'pigging' stations, compressor stations and exposed location single buoy moorings, used in

the offshore petroleum industry for drilling, processing and storage purposes. This international standard applies

to all installations, whether permanent, temporary, transportable or hand-held, to AC installations up to and

including 35000 V and DC installations up to and including 1500 V (AC and DC voltages are nominal values).

DNV-OS-D201: Electrical installations

This offshore standard provides principles, technical requirements and guidance for design, manufacturing and

installation of electrical installations on mobile offshore units and floating offshore installations. The

requirements of this standard are in compliance with relevant parts of SOLAS Ch.II-1 and the IMO MODU

Code. SOLAS references are as quoted in MODU Code 1989 and fulfill class requirements. Note that for

compliance with flag state requirements, later amendments may be applicable.

The standard has been written for general world-wide application. Governmental regulations may include

requirements in excess of the provisions by this standard depending on the size, type, location and intended

service of the offshore unit/installation.

The objectives of this standard are to:

provide an internationally acceptable standard of safety.

defining minimum requirements for offshore electrical installations.

serve as a contractual reference document between suppliers and purchasers.

serve as a guideline for designers, suppliers, purchasers and regulators.

Specify procedures and requirements for offshore units or installations subject to DNV certification and

classification.

NORSOK E-001: Electrical systems

This NORSOK standard contains provisions for electrical installations at all voltages. The standard provides

safety in the design of electrical systems, selection and use of electrical equipment for generation, storage,

distribution and utilization of electrical energy for all purposes in offshore units which are being used for the

purpose of exploration or exploitation of petroleum resources.

This standard does not apply for the electrical installations in rooms used for medical purposes or in tankers.

This NORSOK standard applies to all electrical installations. The installation may be permanent, temporary,

transportable or hand-held, to AC installations up to and including 35000V and DC installations up to and

including 1500V. This standard is also applicable for these voltages, even if a different voltage limit may be

given in some of the parts in the IEC 61892 series of standards. It is expected that the voltage levels in the IEC

61892 series of standards will be corrected as part of the maintenance cycle of this IEC standard. Where this

standard does not give guidelines for systems, equipment and installation for higher voltage level than 11 kV,

reference is made to relevant IEC standards given in annex 2.

The other extensive and important standards for electrical installation, safety, communication and components

are given in annex 2.


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3. Reducing energy losses during transport by increase voltage.

The electrical power that is generated by the wind turbine generators (WTG) will be increased to a higher voltage by

an internal transformer. From these transformers the electrical power will be transported to the transformer substation

through high quality power cables in the seabed. Multiple WTG are linked together, usually about six to seven, to

stabilize the electrical energy and reduce costs of unnecessary cables. Because of these links only a few cables will

arrive in the transformer substation platform. In this substation the voltage of the WTG, usually about 33kV-36kV,

will be controlled and increased further, to about 150kV-250 kV. The output, hundreds of MW, can transport to a DC

converter substation or transported directly to shore. This chapter will explain why increasing the voltage reduces

losses and when using HVDC instead of HVAC.

The total electrical power of a few WTG would be received by the transformer substation platform by one cable. In the

substation the voltage would increase to a higher voltage. By increasing the voltage the losses are less and the

possibility to connect on the grid of many European countries is bigger. The following calculation is to explain the

difference in losses of electrical power by increasing the voltage. The power losses are calculated for two different

single phase voltages over the same cable with the same distance and the same electrical power. For this calculation

the Law of Pouillet would be used, which considers that electrical resistance of a conductor is constant. In reality the

resistance depends on many factors, like temperature and isolation, but that influence is limited. This calculation

proves that the losses are higher when a low voltage is used instead of a high voltage.

U=33kV, Ptot=200MW

Plosses = Rcable * I2 = ((* l) /A) * (P/U)

2

Plosses = Ccable * (P/U) 2

Plosses = 36,731*Ccable MW

U=155kV, Ptot=200MW

Plosses = Rcable * I2 = ((* l) /A) * (P/U)

2

Plosses = Ccable * (P/U) 2

Plosses = 1,665*Ccable MW

It is clear to see that the losses are lower by increasing the voltage. The power is constant, the cable resistance is

constant and the voltage decreases, so the electrical current will increase. The cable losses will increase quadratically

by doubling the current. If the voltage of the example above would be increased from 33kV to 155kV, the losses

would be 22 times less. It is easy to say that the voltage has to be as high as possible, but it is not that simple. It is

impossible to increase the voltage as high as possible because components are made for specified voltages and cables

have to be made much stronger. But HVAC is not the only way to reduce losses.

With HVAC it is possible to transport a maximum power of several hundred megawatt, because HVAC arises reactive

power. HVDC does not arise reactive power because the current direction is constant. HVDC can transport a power of

a few thousands megawatt because of this advantage. In 2008 a group of four people of IEEE presented a technical and

economic analysis to evaluate the benefits and drawbacks of grid connecting offshore wind farms through a DC link. It

concerned a 100MW wind farm. The main part of this article was the sensitivity analysis, as shown in figure 3. There

appears a break-even point of costs for AC and DC transmission when varying the length of the connection. This

break-even point is at a distance of about 90km from offshore substation to onshore substation, where the onshore

substation is a several km out of shore. This break-even-point may fluctuate by commodity prices, by distance between

offshore wind farm to shore and from the distance between shore to onshore substation. More information about

HVDC and this analysis can be found in annex 3.

Figure 3: break-even point HVDC compared to HVAC offshore (source: IEEE Xplore, 2008)


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4. The installation of an offshore transformer substation platform

Offshore transformer substations are used to reduce electrical losses by increasing the voltage and exporting the

power to a convertor substation or directly to shore. Generally a transformer substation does not need to be

installed if the costs of a substation are higher than the costs of the losses. This is in case of a small project, less

than 100MW, or if the connection to the grid is at the collection voltage of 30kV-36kV. Most future offshore

wind farms will be large and/or located far from shore, so the field will require one or more offshore transformer

substations and/or offshore convertor substations. The convertor substation is not situated in every wind farm

because it depends on the distance to shore, so it will not be treated in this chapter. The transformer substation

will contain not only the transformers but also the switchboards of the WTG field, the controlling, cooling

pumps, compensation coils and emergency and utility power supply. In this chapter you will find an analysis of

the offshore transformer substation, which can be used for future projects.

4.1 The transformer substation

The substation platform of today mostly exists of 3 floors: the cable deck, the main deck and the weather deck,

as shown in figure 4.

Figure 4: the transformer substation platform

The cable deck is the lowest deck and contains the smallest components, such as the fuel tanks for emergency

generators and fuel for the helicopter, the switchboard for the WTG-field, batteries/uninterruptible power supply,

most ducts, emergency transformers, workshop container and cooling. This deck is totally closed.

The main deck is situated above the cable deck and is the room where bigger component are placed, such as

main transformers, emergency generators, high voltage switchboards and the air-conditioning/ventilation system.

An emergency accommodation can be found here too. This deck is also totally closed.

The weather deck is the highest deck of the substation. This deck is exposed to the outside and it contains

various sensors and a place for landing of helicopters, because maintenance staff has to be deposited safely.

There is also a possibility to refuel the helicopter.


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4.2 Electrical components of the utility power supply

Offshore transformer substations are used to reduce electrical losses by increasing the WTG-field voltage to

transport voltage. A part of the power from the WTG-field is used for control of the utility power supply

(switches, emergency generators, UPS, transformers etc.). The transformer substation has many (control)

systems for working completely independently and assist in case of short circuit, malfunction component or

another defect in the WTG field. The recommended schematic structure of the utility power supply of a

transformer substation is shown in Figure 5. Which high power systems and components the transformer

substation includes, their functions and how the power have to calculated is explained in 4.2.1. In 4.2.2 the low

power components are explained.

Figure 5: recommended structure transformer substation

The various powers, the various voltage levels and the possible requirements must be known or be selected

before the recommended components could be determine.

The various voltage levels

Voltage Description Common voltage

U1 Voltage of the WTG-field, specified by the builder of the WTG-field 33-36kVAC

U2 Transport voltage. This voltage depends of the destination of the transport voltage. If the

transport cable is connected to a prospective platform, the voltage is free selectable. If

connection is directly to an existing platform or to the grid, the transport voltage is specified

by the existing platform or grid operator.

150kVAC-350kVAC

U3 AC voltage for own use. This voltage is selectable by the substation engineer. It depends of

the working voltage of the large components(pumps, h.v.a.c., crane etc.). and of the total

power of the own use. There is a possibility to use higher voltages like 690VAC/1000VAC

to decrease the current, because some components are limited to a particular current.

400VAC

U4 Voltage for DC components. This voltage depends of the loading voltage of the UPS and

asked voltage of other DC components(communication, security etc.)

220VDC

U5 DC voltage for control. This voltage depends of the working voltage for component control 24VDC/48VDC

U6 voltage of tertiary winding. This voltage depends of the windings of the primary transformer; Explained in


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every transformer is different, so every voltage of a tertiary winding is different. paragraph 4.2.1.3.2

the various power

A document which includes all possible requirements and worst-case scenarios should be drawn. An

explanation and examples of these analyses is given in 4.3.

Power: Description: Calculation & detailing in

paragraph:

Ptotal wtg the total maximum possible power generates by the WTG-field None, known by engineer

of WTG-field

Qreactor the total maximum reactive power that is generating by the shunt reactors 4.2.1.1

Paux. the total maximum possible auxiliary power. 4.2.1.7

Paux. gen. the total maximum power that has to generate by auxiliary generators

(Paux + Plosses aux. trans.).

4.2.1.7

Pown use total minimum and maximum possible power needs for all components of

own use

4.3

Pemer total maximum possible power needs for emergency power 4.2.2.11

Pemer. gen total maximum possible power needs that have to generate by emergency

generator(Pemer + Plosses emer. trans.)

4.2.2.11

Pcomponent AC total maximum possible power needs for AC components. This power

depends of the situation(components which are switched on)

4.3

Pcontrol the total maximum possible power needs for power control. This power

depends of the different situations

4.2.2.13

Pups total maximum power given by UPS after inverter(=Pups supply - Plosses inverter) 4.2.2.9

Pups supply total maximum power given by UPS before inverter 4.2.2.7

Pups asked total maximum power asked by UPS to load it 4.2.2.7

Ptrans total maximum possible power for transport before primary transformer

(Ptotal wtg - Pown use)

4.3

Poutput total maximum possible power for transport after primary transformer

(Ptrans - Plosses prim. trans).

4.3


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4.2.1. High power components

The high power components, which are shown in figure 6, are normally not chosen by HFG Engineering but

mostly by a company specialized in high power components, like ABB, Siemens or Toshiba or another

subcontractor. Because these components are very important for good increase of the power and to prevent

important problems(earth fault, short circuit, capacitive reactive power etc.) they are all performed redundant. It

is necessary to understand how the components are provided and designed before the other part of the utility

power supply could be engineered. It is important to know that al the following calculations are bases on details

after different analysis, without analysis it is impossible to get the wright power. Before the components could

be chosen, an EMTP(Electro Magnetic Transient Program) study is required to explain the complex behaviours

of the power system.

Figure 6: recommended structure high power components

1. Shunt reactors/conductors

With using (HV)AC capacitive reactive power is generated in the electric wires, because its length and its high

voltage works as a capacitor. Because a transformer substation uses a lot of inductive components, like pumps

and generators, an inductive reactive power is also generated. The capacitive and inductive power will partly

neutralize each other, but an part of a reactive power stay exist because the components never neutralize each

other exactly. During low loads (low effective power) and other different situations the reactive power could be a

larger percentage of the effective power (the power factor is lower). This means a very high phase shift which

increases the voltage, current and the losses. To prevent these fluctuations and the power failures that can result,

this reactive power must be compensated and kept in balance.

The function has always been performed by passive elements such as reactors or capacitors, as well as

combinations of the two, that supply inductive or capacitive reactive power. Mostly a substations have to

neutralize capacitive reactive power, so it have to use shunt reactors, the inductive reactive power of the internal

components never neutralize the capacitive reactive power which is generated by the electric wires. These

reactors provide a very high inductive reactive power which is completely counter phase with the residual

capacitive reactive power.


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The shunt reactors have to spread over the WTG-field and the transport wires. For different voltages there are

different shunt reactor systems. The majority of shunt reactors for three phase system voltages of 72,5 kV or

above are in the 30-300 MVAr range and they are normally connected directly to high voltage bus bars or

transmission line ending. For these voltage levels, reactors are most commonly oil-filled type. Future reactors in

the range 72,5-145 kV will tend to be air-core dry-type coil units. Shunt reactors rated below 72,5 kV are either

oil-filled or air-core dry-type units and they are normally connected to the tertiary winding of large power

transformers.

Most fabricators build their own complex shunt reactor system, but most of all are based on 2 different systems.

The winding connection of three-phase reactors or a bank of three single-phase units can be either wye (most

common configuration) or delta, as shown in figure 7. Typically, for system voltages of 72,5 kV or above, the

reactors are wye connected with the neutral grounded directly or through a neutral reactor. For system voltages

below 72,5 kV, the reactors are wye connected with the neutral ungrounded.

Figure 7: Wye & Delta connection of the shunt reactors

For neutralizing reactive power, it is important to know if the reactive power is capacitive or inductive, this

should be known after the EMTP analyse. Shunt reactors are need for neutralizing capacitive reactive power,

conductors for neutralizing inductive reactive power. Once the model has been developed, many scenarios can

be simulated and detailed statistical studies can be performed. In most cases the reactive power that is generated

can be estimated with the formula:

Qreactor = Pmax. gen.* (tan (φdesired) - tan (φsystem) ) var

Pmax. gen. = Maximum generated power (W) = Ptotal wtg or Poutput

φsystem = phi of the current system without neutralising reactive power.

φdesired = phi of the desired system

2. Earth fault protection

This security uses a tertiary winding to ensure that no voltage will pass the neutral point of a transformer or a

generator in case of an earth fault or short circuit in the system. This system limits the fault voltage for a

minimum damage to the switchboards, generators, transformers and control systems. An earth fault protection

limits the current to 108% of the maximum current and can be enabled several times before it needs replacing.

Every transformer in the WTG-field needs one security, so the error is always immediately deleted. The size of

the earth fault protection depends of the voltage, the total power and the maximum current.

Imax = ( Pmax. trans. / (U*cos φ*√3) ) A

Pmax. trans.= Maximum transformed power (W) = Paux. gen. or Pown use


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3. High power transformers

3.1 High voltage step-up transformers for WTG-field voltage to transport voltage

These high power transformers are placed to convert the generated voltage from the WTG-field(U1) to the

transport voltage(U2), to minimize losses. The power demand is distributed over several step-up transformers;

the size of one transformer depends of the total power and the total transformers.

It should be possible that one transformer can be shut down and that the other transformer(s) will take over the

power. It is not desired for the transformers to work at 100%, but at a normal working percentage of 80%.

The power of this three phase transformer can be calculated with the formula

Strans = ( ( (Ptotal wtg –Pown use) / (cos φ) ) / (t-1) )* 1,25 VA

3.2 Tertiary winding or separate step-down transformers for own power supply

The engineer has two choices for own power supply from generated power of WTG-field:

- a tertiary winding from the high power transformers.

- separate transformers directly from the WTG-field voltage.

The choice depends of the requirements of the customer, the total asked power of the (control)systems, the

delivery time of components and the available room. The method of tertiary winding is most used compared to

separate transformers because it is more efficient, cheaper, saving room and suppress harmonics. But a tertiary

winding gives a limited power(maximum of 33% of Ptrans), has a long delivery time, because the primary

transformer has to be prepared, and needs a good early observation of the total asked power of the whole system.

Separate transformers are more expensive, ask more room and induce more losses but have a short delivery time

and selectable power.

- Tertiary winding for own power supply

The voltage of one tertiary winding depends of the total windings of the primary and secondary coil; every

transformer is different, so every voltage of one tertiary winding is different. The best way to select the total

tertiary windings(the more windings the more voltage) is to measure the voltage from one tertiary winding and

compare this with the desired voltage for own use(U3). The voltage from the tertiary winding has to be as close

as possible to the desired voltage to minimize losses. The voltage of the winding(s) has to transform to the

workable and desired voltage(U3) by custom transformers, because the voltage of a tertiary winding is not a clear

voltage.

- Separate step-down transformers for own power supply

These step-down transformers are placed to decrease the voltage from the WTG-field(U1) to the voltage for own

use(U3). The power demand is distributed over several step-down transformers; the size of one transformer

depends of the total power and the total transformers. It should be possible that one transformer can be shut

down and that the other transformer(s) will take over the power. It is not desired for the transformers to work at

100%, but at a normal working percentage of 80%.

The power of a three phase transformer can be calculated with the formula:

Strans = ( ( Pown use / (cos φ) ) / (t-1) ) * 1,25 VA


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3.3 Electrical losses

In both cases there are electrical losses, but a tertiary winding is more efficient. The losses of the separate step-

down transformers are much higher, because the difference between voltage of the WTG-field(U1) and the

workable voltage(U3) is higher compared to the difference between the voltage of the tertiary windings(U6) and

the workable voltage(U3). Summarized the separate transformers has to transform a higher voltage compared to

the tertiary winding transformers, this will result in more losses. These losses are produced in the way of heat,

sound and magnetic dispersion.

4. rectifiers

These rectifiers, using a diode bridge or igbt technology, are placed to convert the own use AC voltage(U3) to

DC voltage for own use(U4). The power demand is distributed over several rectifiers; the size of one rectifier

depends of the total power and the total rectifiers. It should be possible that one rectifier can be shut down and

that the other rectifier(s) will take over the power.

The power of one rectifier can be calculated with the formula Prect. = (Pcontrol+Pcomponent DC) / (t-1) W

Note: There should always be placed a diode-bridge between different DC networks(like UPS-stations) to

suppress harmonics interferences.

5. DC-DC Transformers low voltage (48V)

These transformers are placed to convert the voltage for control to voltage for small component control. The

power demand is distributed over several transformers; the size of one transformer depends of the total power

and the total transformers. It should be possible that one transformer can be shut down and that the other

transformer(s) will take over the power.

The power of one transformer can be calculated with the formula Ptrans = Pcontrol / (t-1) W

Note: There should always be placed a diode-bridge between different DC networks(like DC transformers) to

suppress harmonics interferences.

6. High voltage switchboards transport voltage and WTG-field voltage

The switchboards (not shown in figure 6) are used for control of the connections between WTG-field to

transformer substation, the connections between the internal components and systems, the connections between

substation to land or from substation to another substation. It is recommended to perform important components

like switchboards redundant with using components of two different series or different producers to be sure that

each connection would disconnect(extra safety). Every connection to the substation has to have two different

connections, namely a normally closed and a normally open, to avoid any possibility of construction defects.

If the power is too high, the current will exceed the current limit of the switchboard. If the current on the

switchboard is too high, a component or switchboard could be damaged. In this case the switchboard will have to

be replaced by a bigger one, which has a higher current limit, or the voltage has to increase which occurs to a

change of voltage level U3. The maximum current depends of the size of the switchboards, how larger the

switchboard how higher the maximum possible current but how higher the price is. The different fabricators of

switchboards have scalable types, but 5000A is the limit for control switchboards. The choice depends of the

total power, current and voltage:

Imax = (Pmax. trans. / (U*cos φ*√3) ) A


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7. Auxiliary generators WTG-field

If the WTG-field does not generate power(because there is too much/too little wind or there is a short

circuit/maintenance on the transport line) several diesel driven auxiliary generators generate power for substation

power use. This power is need for the WTG internal electrical systems (U1) and the control systems of the

substation (U3). It should be possible that one generator can be shut down and that the other generator(s) will

take over the power.

Buying the best or cheapest available generator without any other consideration is clearly not the best approach.

If the appropriate generator is chosen there will be no unexpected system failures, no shutdowns due to capacity

overload, increased longevity of the generator, guaranteed performance, smoother hassle-free maintenance,

increased system life span and assured personal safety. To get these benefits you have to delve deep into your

power generation requirements before making a choice. It is possible with the questions and operations on the

next page.

- What are the items that need to be powered by the auxiliary generator? For substations this are most of the time

the switchboards, pumps, instrumentation, control, radar, radiotelephone, intercom, camera system, alarm

system, lighting etc. But it is possible that more systems have to be constant power or that other systems can be

shut down. This is specified in the worst case scenarios (paragraph 4.3).

- Enumerate the starting and running wattage of all the respective items. Getting the right starting and running

wattage of the devices you intend to power is crucial for calculating the accurate power requirements. Normally,

you will find these data in the identification plate or the owner's manual in the buyer's kit of each respective

device, tool, appliance or other electrical equipment. The total power of all components and systems to control

the substation and WTG-field is also known as Pown use. Because there are different situations the needed power is

different. An example, at worst case, that means no power from WTG-field to substation, Paux=Pown use. This

worst case is also the minimum power requirement for the auxiliary generators, but this is explained in 4.3.

- Define the total generators and calculate the minimum power requirements and with formula

Saux. gen. = ( ( (Paux + Plosses aux. trans.) / cos φ) / (t-1) VA

Plosses aux. trans = known by generator fabricator

8. Step-up transformers for auxiliary generators

These transformers are placed to increase the voltage from the auxiliary generators to the WTG-field voltage(U1)

for internal use. The power of the auxiliary generators have to be distributed over several step-up transformers;

the size of one transformer depends of the total power of the generators and the total transformers. It should be

possible that one transformer can be shut down and that the other transformer(s) will take over the power of all

auxiliary generators. It it is not desired for the transformers to work at 100%, but at a normal working percentage

of 80%.

The power of one auxiliary step-up transformer for a auxiliary generator can be calculated with the formula:

Saux. trans =( Saux. gen. / (t-1) ) * 1,25 VA


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4.2.2. Control and uninterruptible power supply

The low power components are recommended and engineered by HFG Engineering, as shown in figure 8. Some

of these components are that important to prevent the most important problems on a substation, namely a black-

out. The installation below provide emergency power supply, uninterruptible power supply and power control.

As opposed to the high power components these are not always performed redundant.

Figure 8: control and uninterruptible power supply

9. UPS

There are several UPS-stations placed for intercepting voltage spikes, voltage drops, brown outs and black outs.

At this way the power supply for the essential consumers will never be disturbed or interrupted. The UPS will

also fill up the power gap between no power generating of the WTG (no wind/too much wind or ) and power

generating by the generators.

The size of the UPS depends of the total power of the systems and the total time of a voltage gap. The desired

power have to be supplied by several UPS stations; it should be possible that one UPS-station can be shut down

or fail and that the other UPS station(s) will supply the power. There should be placed diode links between the

different UPS-stations to reduce harmonic distortion because an UPS-station will be generating DC. You have to

delve deep into your power generation requirements before making a choice of the size of the UPS station. The

power of one UPS-station will be calculating with the following actions.

- What are the items that need to be powered by the UPS? What is the maximum power that is needed?

For substations these are most of the time the switchboards, instrumentation, control, radar, radiotelephone,

intercom, camera system, light security, alarm system and instrumentation. But it is possible that more systems

have to be constant powered. The choice of switch off systems in certain situations are explained in the worst

case scenarios(paragraph 4.3).

- What is the minimum time that an UPS-station has to produce full power?

This depends of the total power(Pown use) that is need to fill up the gap between no power from WTG-field and

power generated by emergency generators. An example, if the total power for the essential control systems is

1kW and the gap is 1min, one UPS station needs a minimum power of 500 W/min(in case of two UPS stations).

- Calculate the total power requirements and define the total UPS-stations with formula:

Pups supply = Pmax / (t-1) W


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10. inverters

There are only inverters, using igbt-technology, placed for converting the DC voltage from the UPS to the AC

voltage for own use(U3). There are at least two UPS-stations and two transformers placed for excluding every

possibility of power failure. The power demand is distributed over several inverters; the size of one inverter

depends of the total power and the total inverters. It should be possible that one inverter can be shut down and

that the other inverter(s) will take over the power.

The power of one inverter can be calculated with the formula Sinv. = (Pups supply / cos φ) / (t-1) VA

Note: There should always be placed a diode-bridge between different DC networks(UPS-stations) to suppress

harmonics interferences.

11. Emergency generators

If there is no power from the WTG-field, the auxiliary generator supply fails and no power is available from the

UPS the emergency power must be provided to maintain all essential loads. Because the probability of failure of

the both auxiliary generators is almost 0%, one diesel driven emergency generator have to be installed to supply

the emergency switch board. This generator is not redundant.

Buying the best or cheapest available generator without any other consideration is clearly not the best approach.

If the appropriate generator is chosen there will be no unexpected system failures, no shutdowns due to capacity

overload, increased longevity of the generator, guaranteed performance, smoother hassle-free maintenance,

increased system life span, much smaller chance of asset damage and assured personal safety. To get these

benefits you have to delve deep into your power generation requirements before making a choice with using the

ESD. It is possible with the following questions and operations.

- What are the components that need to be powered by the emergency generator? For substations these are most

of the time the same components powered by the UPS, like switchboards, instrumentation, control, radar,

radiotelephone, intercom, camera system, lighting, security, alarm system and instrumentation. But it is possible

that less or more systems have to be powered by the emergency generator.

- Enumerate the starting and running wattage of the respective items. Getting the right starting and running

wattage of the devices you intend to power is crucial for calculating the accurate power requirements. Normally,

you will find these data in the identification plate or the owner's manual in the buyer's kit of each respective

device, tool, appliance or other electrical equipment.

- Calculate the total power requirements and define the total generators with formula

Sgen = ((Pemer+ Plosses emer. trans) / cos φ) / (t-1) VA

Plosses emer. trans = known by generator fabricator(mostly 1-5% of input power)


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12. Transformers for emergency generators

If the voltage of the emergency generator is not the same as the voltage for own use(U3) a transformer for the

emergency generator is needed. This transformer is placed to convert the voltage from the emergency generator

to the own use voltage(U3). Because there is only one emergency generator (a second emergency generator will

never be used) the power demand have to be distributed over a single transformer. Normally it is not desired for

the transformers to work at 100%, but at a normal working percentage of 80%.

The power of one transformer can be calculated with the formula

Strans = (Pemer / cos φ) * 1,25 VA

13. Control systems (fire protection, communication, radar, intercom, camera system, lighting security,

alarm system, instrumentation etc.)

The group named ―utility power supply control systems‖ is very important for the constant power of the

substation, but also for constant power of communication and safety systems. Some systems have to be constant

powered while other systems can be shut down in case of an emergency. Mostly this choice depends of the

legislation and safety laws of four different platform possibilities:

Not dependent manned platform

This platform is manned and not dependent of other platforms, so the communication from shore,

vessels and aircraft to the substation is directly without the intervention of another substation.

Not dependent unmanned platform

This platform is unmanned and not dependent of other platforms, so the communication from shore,

vessels and aircraft to the substation is directly.

Dependent unmanned platform

This platform is unmanned and dependent of other platforms, so the communication from shore, vessels

and aircraft to the substation is indirectly.

Dependent manned platform

This platform is manned and dependent of other platforms, so the communication from shore, vessels

and aircraft to the substation is indirectly.

Most offshore windfarm transformer substations will be specified as a not dependent unmanned platform, but it

is possible that this will change in the future(more substations in one WTG-field). For these kind of platforms

there are specified (control) systems that have to be installed. A lot of these systems are described in standards

and laws, as treated in chapter 2.

There are different systems needs on the different platforms. Because most substations are specified as a not

dependent unmanned platform, only systems for this type will specified. The power Pcontrol is the total power of

all the systems that are specified in this paragraph, because in case of maintenance this

Cooling

Cooling systems are one of the most important systems of a not-dependent unmanned platform. The different

systems and components generating a lot of heat and will damage if there is no cooling. Seawater will be used to

cool these systems and components, so seawater cooling pumps, seawater lift pumps and filtering systems will

be need. For some components air-cooling is sufficient.


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(Tele)communication and radio equipment

Because most offshore wind farm substations are specified as an unmanned platform, most communication and

radio systems have to be enabled if someone is on the platform for inspection and maintenance. The systems that

have to be installed on a unmanned platform are different radio and communication systems.

Radio systems

- Maritime VHF with DSC, it is used for a wide variety of purposes, including summoning rescue services and

communicating with shore.

- Aeronautical VHF communication system, for communication with helicopters.

- GMDSS handheld, portable GMDSS communication for the whole substation.

Communication equipment

- Radar

- Intercom

- Camera system(cctv)

- Private automatic branch exchange(PABX)

- Telephones

Fire and emergency protection

There are several systems installed in a substation to protect it to fire and in case of an emergency, thinking of

fuel pumps, alarm systems(PA/GA) and fire fighting systems. These systems have to be 24/7 control and standby

for fire or emergency’s.

Meteorological equipment Navigation Aids System

A not dependent substation have to be visible at all weather conditions. At least the following systems have to be

installed on the platform and enabled if the situation needs it. A control panel will control all these components.

- Fog horn

- Lantern

- Heli-deck lighting

- Crane cabin and boom lanterns

- Several floodlight

Instrumentation

The instrumentation of a substation will control all the previous components and systems but also small power,

pumps, h.v.a.c. and lighting for the accommodation of a substation. The control of these components depends on

its quantity. An analysis(like electrical load analyse, HAZID & HAZOP) should be made, where the failure rate,

mean time between failure & repair, downtime, probability of failure on demand, common cause failure,

quantitative risk analysis and other component properties should be included. These should give a good view of

the quantity of different components; redundancy could be considered if the quantity is too bad. After this risk-

analysis the Emergency Shutdown System(ESD) system for instrumentation is known. The ESD is designed to

minimise the consequences of emergency situations. In case of a fire, an accident, a changing of the situation, as

mentioned in paragraph 4.3, or a total black-out this system makes the choice to shut down particular systems to

avert different (dangerous) situations. The ESD does not include the operating philosophy, which describes the

control of components


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4.3 Worst-case scenario’s

There are several situations where the substation should remain function. Some systems have to be constant

powered while other systems can be shut down in case of emergency. This is specified in an ESD system. The

ESD system ensures which systems may fall out in different cases. So in case of fire or explosion, parts of the

plant may fall out.

There are four situations where the substation should remain function This four different weather and component

situations are:

Normal situation

Wind situation

Maintenance or short circuit situation

Malfunction component situation

A general overview to determine when a substation(unmanned not-dependent platform) is in a particular

situation and its consequences, is given in figure 9.

Figure 9: recommended flow chart different situations


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Every situation has other priorities and other consequences for different systems and components. In the

following explanations the differences between the situations becomes clear.

Normal situation

Enough wind

— WTG-lines will start up one by one.

— Power for starting up WTG-field and power supply for substation is taken from the grid.

— All WTG-lines are generating power.

— Substation will use a part of the generated power from the WTG-lines for internal power use. The rest

of the power will be distributed to the onshore grid.

Wind situation

Too much wind/storm

— All WTG-lines are in idling mode or standstill. At this situation they are not generating power.

— The power for internal control systems of WTG and substation comes from power take from the

onshore grid.

Not enough wind

— As long as the generated power is enough (Ptotal wtg ≥ Pown use) for internal systems of WTG and

substation, the installation still works as normal situation.

— If generated power is not enough (Ptotal wtg ≤ Pown use) for internal control systems for WTG and

substation, power supply comes from power take from the onshore grid.

Maintenance or short-circuit situation

Maintenance or short circuit transport line (from offshore substation to onshore substation)

All WTG-lines in idling mode or standstill, controlled by substation. Substation has to compensate the voltage

for the internal control systems.

— Directly after close transport line UPS switch on and auxiliary and/or emergency generators will start,

as given in figure 10(next page).

— If a generator is started and enough power is generated, shut down fully power generating of UPS.

Maintenance or short circuit WTG-field

— The WTG-lines which contains short-circuit and/or need maintenance have to set in idling mode or

standstill, controlled by substation.

— If not enough power is generated by other WTG-lines, auxiliary or emergency generators will generate

power for substation as in figure 10(next page). If other WTG-lines are still generating power, the

substation works as in normal situation.


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Figure 10: recommended flow chart for start generators

Malfunction component situation

Malfunction component on WTG-line

— The WTG-lines which have malfunction of a component have to be set in idling mode or standstill,

controlled by substation. Repair by technicians is directly needed.

— If not enough power is generated by other WTG-lines, auxiliary or emergency generators will generate

power for substation as in figure 10. If other WTG-lines are still generating power, the substation works

as in normal situation.

Malfunction component on Substation

Component is redundant

— Because the most important components of the substation are executed redundant, as mentioned in

paragraph 4.2, the system will keep working in case of a malfunction of a component. If a component is

damaged, malfunctioning or defect the redundant component is taken over the whole power. Repair of

the component is needed but the substation will still working.

Component is not redundant

— Some of the utility power supply parts are not executed redundant because they have a probability of

failure of nearly 0% or it is not that important to execute redundant(like hot water pump for

accommodation). It is recommended to analyse the parts as mentioned in paragraph 4.2, with risk-

analysis like HAZID, HAZOP etc. These analyses shows components and/or systems that have to be

performing redundant because they are very important or have a high probability of failure.


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Conclusion

The construction, calculation and redundancy of components of the utility power supply were subjects of many

discussions, problems and adjustments during engineering and building of previous substation projects. For these

discussions, problems and adjustments this report is a guideline because in this report the utility power supply

part of a transformer substation for offshore wind farms is investigated in detail. In this guideline you will find

the recommended structure of a substation and was made after a few studies. The conclusions of these studies

are:

increasing the voltage will reduce losses. The cable losses(=resistance) will increase quadratically by

doubling the current. This resistance depends on many factors, like temperature and isolation, but that

influence is limited.

an enumeration of the legislation of an offshore substation is known. There are several standards for the

company, general standards for offshore substations and guidelines for the electrical installation which

are very important. The most important standards describes the requirements of the whole substation.

The advantages and disadvantages of HVDC compared to HVAC and the break-even point of costs for AC

and DC transmission when varying the length of the connection are known. HVDC will be cheaper

compared to HVAC after 90km between the substations.

After these studies the components of such a transformer substation could be chosen. The choice of these

components depends of many factors, such as performance, quantity and redundancy. The choice of redundancy

depends of several analyses: HAZID, HAZOP and EMTP. The recommended structure of the offshore

transformer substation is made with using these analyses and conclusions.

This guide for the utility power supply part of a transformer substation for offshore wind farms will result to:

a good explanation to determine the various voltage levels.

an explanation, calculation and determination of the power of the different components.

which influences on components take into account.

the various worst-case scenarios, which a substation has to deal with, are known and a scenario could be

determined.

different outside power supply opportunities, like power taken from grid and power taken from wind

turbines, are known and could be determined.

different own power supply opportunities, like auxiliary generator, emergency generator and UPS, are

known and could be calculated.


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Recommendation

In this report the utility power supply parts, which take care of the electrical power of components in different

situations, of such a transformer substation is investigated in detail. The structure, welding, testing, ground

investigations and the size and pricing of components are not treated in this report.

To get a clear picture of the utility power supply of a substation it is recommended to:

— investigate the possibilities for ―clean‖ energy production for own power supply in case of no wind. In

a ―clean‖ wind farm a diesel generator is not desired, but still necessary now. Is it possible to get a

―clean‖ solution for auxiliary or emergency supply, in case of polluting diesel-generators?

— compare other properties of components, such as weight distribution, assembling and heat emission of

different fabricators. Is it possible to buy smaller, more efficient or cheaper components?

— investigate the cost-benefit of the recommended structure. Is it competitive compare to other substation

fabricators?

— investigate the utility power supply of convertor substation(HVDC substation).


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Date: 8/6/2011

List of used parameters

U = voltage(V)

I = current(A)

P = power(W)

= density(kg/m3)

Qreactor = Minimum reactive power of one shunt reactor(var)

Strans = Minimum power of one transformer(VA)

Sgen = Minimum apparent power of one generator(VA)

Ptotal wtg = total maximum possible power generates by the WTG-field(W)

Poutput = Maximum power after increasing voltage(W)

Pcontrol = total maximum possible power needs for power control(W)

Pups = total maximum power given by UPS after inverter(W)

Pcomponent AC = total maximum possible power needs for AC components(W)

Pcomponent DC = total maximum possible power needs for DC components(W)

Pups supply = total maximum power given by UPS before inverter(W)

Pups asked = total maximum power asked by UPS to load it, known by UPS fabricator(W)

Paux. = total maximum possible power needs for auxiliary power(W)

Paux. gen. = total maximum possible power needs that have to generate by auxiliary generator(W)

Pown use = Maximum power used by substation components(W)

Pemer = total maximum possible power needs for emergency power(W)

Pemer. gen. = total maximum possible power needs that have to generate by emergency generator(W)

Pmax. trans. = Maximum transformed power (W)

Cos φ = Power factor. The network code of the network operator prescribes a power factor between 0,80 and

1,0 for generation units connected to networks with a voltage of 50kV and higher measured at the generator

terminals. With voltage lower than 50kV, like WTG-field voltage, the power factor have to be between 0,85 and

1,0.

t = total of components

φsystem = phi of the system without using shunt reactors/conductors

φdesired = phi of the desired system


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Date: 8/6/2011

Glossary

Utility power supply = the provision which ensures that systems and components of the substation gets constant

voltage.

Top side = Upper part of a fixed installation which sits on top of the jacket and consists of the decks,

accommodation and process equipment.

Jacket = Steel framework used to support platform topsides.

WTG = Wind Turbine Generator(s).

Sustainable energy= energy that is be generated and consumed without any significant negative impact to the

environment.

Nacelle = the housing on the top of the mast.

MW= Mega Watt (1000 kW or 1000000 Watt).

Transformer substation platform = on this platform the voltage would be increase or decrease.

Convertor substation platform = on this platform the voltage would be changed from AC to DC or vice versa.

Using this substation longer distances and larger capacities may possible.

AC = Alternating Current.

DC = Direct Current.

HVAC = High Voltage Alternating Current.

h.v.a.c. = heating, ventilation and air conditioning.

HVDC = High Voltage Direct Current.

Capacitive reactive power = the part of the power that occurs in capacitors and very long cables.

Inductive reactive power = the part of the power that occurs in magnetic fields.

Effective power = the real power that is useful.

EMTP = Electro Magnetic Transient Program

HAZID = A hazard identification study.

HAZOP = A hazard operability study.

IEEE = Institute of Electrical and Electronics Engineers, an association which is dedicated to advancing

technological innovation and excellence for the benefit of humanity.

NWEA = North West Wind Energy Association.

EN= European Standards (EN) are documents that have been ratified by one of the 3 European Standards

Organizations CEN, CENELEC or ETSI and by national standard organizations as DIN, NEN or BSI.

CENELEC = An European committee for electro technical standardization which works with 15,000 technical

experts from 31 European countries.

NORSOK= NORSOK standards will be used to provide the Norwegian oil & gas industry input to the

international standardization process and development and publication of international standards.

NEN = Dutch Standardization Institute.


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Date: 8/6/2011

DIN = German Standardization Institute.

DNV = Det Norske Veritas. A global provider of services for managing risk , helping customers to safely and

responsibly improve their business performance.

GL = Germanischer Lloyd, a German Institute for Standardization, originated from four shipping companies.

BSI = British Standards Institution.

ISO = International Standard Organization.

IEC = International Electrotechnical Commission, a worldwide International Commission for Electrotechnical

standards.

IALA=International Association of Marine Aids to Navigation and Lighthouse Authorities

ESD = Emergency Shutdown System, a design to minimise the consequences of emergency situations.

IGBT = Insulated Gate Bipolar Transistor. A three-terminal power semiconductor device, noted for high

efficiency and fast switching.

Thyristor = a solid-state component used to switch and control electric current flow.

Redundancy = duplication critical components of a system with the intention of increasing reliability of the

system.

Fault protection = protection of fault in the connection of electrical parts.

UPS = Uninterruptible power supply.

Black out = Complete failure of voltage for a long time.

Brown out = A temporarily decrease of the voltage, longer than 1 second.

failure rate = the frequency with which an engineered system or component fails.

mean time between failure & repair = the time between a system failure and the repair of that same system.

downtime = the period that a component would not function in case of a failure.

probability of failure on demand = the frequency that a failure occurs when the device is expected to provide

service.

common cause failure = errors with a common cause. One error provides all components of the same type(same

producer, year etc.) to fail.

quantitative risk analysis = To provide an overall assessment about whether the project is likely to achieve its

objectives when all risks are considered simultaneously.

ALARP = As Low As Reasonably Practicable

Cctv = Closed-Circuit Television

GMDSS = Global Maritime Distress and Safety System

PA/GA = Public Address and General Alarm System

http://en.wiktionary.org/wiki/Component

http://en.wikipedia.org/wiki/System


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Date: 8/6/2011

References

The Dutch Ministry of Infrastructure and the Environment

Dutch Standardization Institute (NEN)

HVDC Connection of Offshore Wind Farms to the - Paola Bresesti, Wil L. Kling, Ralph L. Hendriks,

Transmission System Riccardo Vailati(IEEE)

Helwin & Dolwin Offshore Converter Substation - ABB

Net code Electricity 11 january 2011(Energiekamer) - Dutch Competition Authority (NMA)

http://www.nwea.nl - Dutch Wind Energy Association (NWEA)

Wind Energy – The Facts (isbn: 978-1-84407-710-6) - European Wind Energy Association (EWEA)

BSH Standard Design of Offshore Wind Turbines - Maritime and Hydrographic Company (BSH)

Shunt reactors in power systems - Areva T&D 2007


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Date: 8/6/2011

Annex 1: Project Management Document(in Dutch)

PROJECT

MANAGEMENT DOCUMENT

Afstudeerproject: Utility Power voorziening voor offshore windfarms substations

Versie: 1.3

Startdatum: 31 januari 2011

Einddatum: 24 juni 2011

Opsteldatum: 17 febr. 2011

Accoord Bedrijf: Accoord Hogeschool: Student:

Dhr. Tillema, HFG Engineering Dhr. Voermans, Avans D.Hermus

Dhr. Van der Heijden, HFG Engineering


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Date: 8/6/2011

0. Uitvoeringsgegevens

Bedrijfsgegevens: Naam van de organisatie : HFG engineering

Adres : Noordweg 8

Postcode/plaats : 3336 LH Zwijndrecht

Telefoonnummer : 31 (0)78 6250525

Bedrijfsbegeleiding Naam begeleider : dhr. van der Heijden

E-mail adres : [email protected]

Telefoonnummer :+31(0)78-6250265 / +31(0)6-51924371)

Naam begeleider : dhr. Tillema

E-mail adres : [email protected]

Telefoonnummer :+31(0)78-6250455 / +31(0)6-10955165)

Onderwijsinstelling: Avans Hogeschool, Academie voor Technologie en Management

Adres : Lovensdijkstraat 61-63

Postcode/Plaats : 4818AJ Breda

Telefoonnummer : Receptie (076) 525 05 00

Postadres : Postbus 90.116, 4800 RA Breda

Hogeschoolbegeleiding: Naam begeleider : Harry Voermans

E-mailadres : [email protected]

Student: Naam :D. Hermus

Studentnummer :2001930

Adres :kruislandseweg 6

Postcode/plaats :4724SM Wouw

Telefoonnummer :0165-300112 / 0612363710

E-mailadres :[email protected]


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Date: 8/6/2011

1. Situatiebeschrijving

bedrijfskarakteristiek (branche, geschiedenis, financiën, organisatie).

In 1948 begon Heerema als een klein bouwbedrijf in de buurt van Maracaibo in Venezuela. Sinds dit

begin is Heerema toegenomen in reikwijdte, omvang en technische bekwaamheid van haar

activiteiten. In het begin van de jaren ’80 heeft Heerema haar diensten uitgebreid naar de Noordzee en

is zich toe gaan spitsen op de offshore olie en gas industrie. Hierbij is de fabricage werf in Vlissingen

geopend, toen nog Heerema Havenbedrijf hetend. Hierna groeide het bedrijf snel en zijn Grootint(Nl,

Zwijndrecht) en Tønsberg(No), overgenomen. De laatste vestiging is in 2005 door dalende vraag

gesloten.

In 1990 is de Heerema Fabrication Group BV opgericht zodat alle fabricageactiviteiten van de

Heerema groep duidelijk worden beheerd. In 1995 is een werf, Heerema Hartlepool Ltd, geopend in

Hartlepool(GB). In 2003 veranderde de naam van de werf in Vlissingen, Heerema Havenbedrijf B.V.,

naar Heerema Vlissingen BV en de werf in Zwijndrecht, Grootint, naar Heerema Zwijndrecht B.V.

Begin 2009 is een werf, HFG Polska SP, in het zuiden van Polen geopend waarbij het aantal

vestigingen van Heerema Fabrication Group op 4 uitkomt.

product, dienst, assortiment

Heerema Fabrication Group is een toonaangevende engineering en fabrication contractor op het gebied

van complexe constructies voor de offshore olie & gasindustrie en windenergie. HFG bouwt o.a.

platforms waarvan zowel de jackets en topsides en offshore substations voor offshore

windenergieparken in de Noordzee. HFG Engineering zorgt voor de engineering van deze projecten.

markt(en)

Heerema Fabrication Group streeft naar het worden van de meeste gerenommeerde EPC(I) aannemer

voor grote, complexe staalconstructies voor klanten in de offshore olie & gas en energie industrie.

beleid (huidige beleidsdoelen)

HFG biedt innovatieve engineering oplossingen en een sterk projectmanagement. HFG heeft een

sterke marktpositie en wilt deze altijd versterken, waaronder de veiligheid nooit tekort mag komen.

Een belangrijk aspect van de Heerema Fabrication Group is ook één van de bedrijfsmotto’s: we

werken veilig of we werken niet.

probleemstelling voor het project

Op de werven van Heerema in Vlissingen en Hartlepool(UK) zijn een aantal Offshore Substations

gebouwd. Bij deze Offshore Substations was de Utility Power Voorziening onderwerp van

regelmatige discussie en aanpassingen.

afbakening project (systeemgrenzen)

Onderzoek naar de Utility Power Voorziening voor Offshore Windfarm Substations ten behoeve van

toekomstige projecten zodat een leidraad voor deze voorziening kan worden gegeven.


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Date: 8/6/2011

2. Doelstelling

Het eindproduct van dit project is een duidelijke omschrijving waar de Utility Power Voorziening

voor Offshore Substations bij Windfarms aan dient te voldoen qua wetgeving, stroomvoorziening en

de worst-case scenario zodat dit niet meer zorgt voor discussies en aanpassingen tijdens toekomstige

projecten.

Het eindproduct is opgedeeld in een drietal subdoelen.

Subdoel 1: Beschrijven van de algemene opbouw voor windfarms, zoals de diverse spanningskeuzes,

transport van de vermogens en de toekomst van windfarms/groene energie. Hierbij wordt vooral een

uitleg gegeven over het toenemend gebruik van windfarms.

Subdoel 2: Voormalig gebouwde windfarm projecten bestuderen, waaronder Borwin Alpha, Dolwin

Alpha, Greater Gabbard en Sheringham Shoal. Daarna toespitsen op het substation waarbij

componenten- en vermogensanalyse gemaakt moet worden. Deze analyses hebben als doel om te

bepalen bij welke componenten de prioriteiten in het substation liggen, redundantie en faalkans van

componten dienen hierbij ook te worden meegenomen. Uiteindelijk dienen er worst-case scenario’s te

worden beschreven en de reacties met betrekking tot de Utility Power Voorziening hierop.

Aanbevelingen met betrekking tot verbeteringen van substation dienen hierin mee te worden genomen.

Dit subdoel dient enkel toegespitst te worden op de elektrische systemen, construction & structural

e.d. worden hierbij dus buiten beschouwing gelaten.

Mijlpaal 1 april: oplevering van het tussenverslag aan het bedrijf en de hogeschool. Hierbij zijn

subdoel 1 en 2 (gedeeltelijk) behandeld. Naar aanleiding van dit rapport vindt ook een tussengesprek

tussen de student en de bedrijfsbegeleider plaats zodat het bedrijf en de stagaire eventuele

(miscommunicatie)problemen op kunnen lossen en om de vorderingen te bespreken. Tevens vind in

deze periode ook de terugkommiddag op Avans Hogeschool plaats zodat de vordering tussen student

en begeleider kunnen worden besproken.

Subdoel 3: Uitzoeken welke internationale, Europese en nationale wetgeving en richtlijnen op een

offshore substation van toepassing zijn. Dit dient een goed en duidelijk overzicht te geven zodat een

leidraad voor HFG Engineering wordt ontwikkeld. Deze dient vooral toegespitst te worden op de

elektrische systemen en instrumentatie.


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Date: 8/6/2011

4. Relevante documenten

Diverse documentatie aangeleverd door het stagebedrijf.

5. Werkzaamheden

Werkzaamheden subdoel 1: Het geven van de algemene opbouw van windfarms en de uitleg voor

het toenemend gebruik van windfarms wordt gedaan aan de hand van informatie die te vinden is op

het internet, studieboeken en lesmateriaal, diverse gesprekken met personeel van stagebedrijf en

literatuur van een voormalig projecten dat wordt aangeleverd door het bedrijf. Dit zal vooral een

inleiding en uitleg geven zodat het toenemend gebruik van windfarms wordt verklaard.

Werkzaamheden subdoel 2: Voormalig gebouwde windfarm projecten bestuderen, waaronder

Borwin Alpha, Dolwin Alpha, Greater Gabbard en Sheringham Shoal. Deze informatie wordt gehaald

uit de toegeleverde literatuur en projectinformatie.

Daarna toespitsen op het substation waarbij componenten- en vermogensanalyse gemaakt moet

worden. Deze analyses hebben als doel om te bepalen bij welke componenten de prioriteiten in het

substation liggen, redundantie en faalkans van componten dienen hierbij ook te worden meegenomen.

Deze analyses worden gemaakt aan de hand van de toegeleverde literatuur en gesprekken met

personeel van het stagebedrijf die over de kennis beschikt.

Uiteindelijk dienen er worst-case scenario’s te worden beschreven en de reacties met betrekking tot de

Utility Power Voorziening hierop. Aanbevelingen met betrekking tot verbeteringen van substation

dienen hierin mee te worden genomen.Dit gedeelte vraagt vooral kennis die is opgedaan tijdens de

opleiding. Dit subdoel zal, in combinatie met de overige subdoelen, uiteindelijk tot de conclusie en

eindresultaat leiden.

Werkzaamheden subdoel 3: Internationale, Europese en nationale wetgeving en richtlijnen van een

offshore substation bepalen zodat een leidraad voor HFG Engineering kan worden ontwikkeld. Hierbij

wordt gebruik gemaakt van de toegeleverde literatuur, internet, personeel van het stagebedrijf, contact

met overheidsinstanties en andere bedrijven. Uiteindelijk moet dit voor HFG Engineering een leidraad

voor substations van windfarms opleveren.


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Date: 8/6/2011

6. Eisen (randvoorwaarden)

Externe voorwaarden

De opdracht dient individueel te worden uitgevoerd.

De opdracht sluit aan bij de persoonlijke afstudeerdoelen.

De opdracht past binnen de context van de opleiding.

De opdracht vloeit voor uit een reeële behoefte van de organisatie en is dus zinvol.

De opdracht heeft actualiteitswaarde.

De opdracht is voldoende complex en passend bij de werkzaamheden van een HBO’er.

De opdracht is duidelijk afgebakend en levert een afgerond geheel op.

De opdracht vereist integraal denken.

De opdracht vereist een hoge mate van zelfstandigheid van de student.

De opdracht moet redelijkerwijs binnen de afstudeerperiode afgerond kunnen worden.

Functionele eisen

Het tussen en eindrapport dienen beide bij het bedrijf en bij de hogeschool te worden ingeleverd. Het

eindrapport dient naast in het Nederlands ook in het Engels te worden opgeleverd. Dit vanwege de

internationale marktpositie van het bedrijf.

Afbreukrisico

Bij het opleveren van het tussenverslag kan door het stageverlenende bedrijf worden bekeken hoe dat

de vorderingen van de student zijn. Naast de wekelijkse gesprekken kan ook hierbij worden

ingegrepen als de student de verkeerde kant op is gegaan of dreigt te gaan.

7. Kwaliteitsbewaking De werkzaamheden worden wekelijks besproken met de bedrijfbegeleider. Als er zich problemen

voordoen kan ook op de bedrijfsbegeleider aanspraak worden gemaakt, indien deze aanwezig is(i.v.m.

meerdere verstigingen en gesprekken toeleveranciers). Tevens kan er ook hulp worden gevraagd bij

personen waarvan de stagaire te horen heeft gekregen dat deze de juiste kennis hebben. Mocht er zich een

dringend probleem voordoen dan kan er altijd contact op worden genomen.

De schoobegeleider wordt door middel van een 2 wekelijkse logboek op de hoogte gehouden van de

vorderingen van de student. Zo kan de schoolbegeleider toezien op de vorderingen van de student en kan

hij inschakelen als blijkt dat de student te ver op de planning achterloopt.


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Date: 8/6/2011

8. Tijd (planning) Voor het eindproduct zijn 20 weken ingedeeld waarvan 1 week mogelijke uitloop en 1 week

presentatievoorbereiding. De tijd die voor elk subdoel staat is het percentage dat gegeven staat over

18 weken, 10% staat dus voor 1,8 week oftewel 9 dagen/72 uur.

Subdoel 1: Beschrijven van de algemene opbouw voor windfarms, zoals de diverse spanningskeuzes,

transport van de vermogens en de toekomst van windfarms/groene energie. Hierbij wordt vooral een

uitleg gegeven over het toenemend gebruik van windfarms.(25% van totaal)

Subdoel 2: Voormalig gebouwde windfarm projecten bestuderen, waaronder Borwin Alpha, Dolwin

Alpha, Greater Gabbard en Sheringham Shoal. Daarna toespitsen op het substation waarbij

componenten- en vermogensanalyse gemaakt moet worden. Deze analyses hebben als doel om te

bepalen bij welke componenten de prioriteiten in het substation liggen, redundantie en faalkans van

componten dienen hierbij ook te worden meegenomen. Uiteindelijk dienen er worst-case scenario’s te

worden beschreven en de reacties met betrekking tot de Utility Power Voorziening hierop.

Aanbevelingen met betrekking tot verbeteringen van substation dienen hierin mee te worden genomen.

Dit subdoel dient enkel toegespitst te worden op de elektrische systemen, construction & structural

e.d. worden hierbij dus buiten beschouwing gelaten.(40% van totaal)

Mijlpaal 1 april: oplevering van het tussenverslag aan het bedrijf en de hogeschool. Hierbij zijn

subdoel 1 en 2 (gedeeltelijk) behandeld. Naar aanleiding van dit rapport vindt ook een tussengesprek

tussen de student en de bedrijfsbegeleider plaats zodat het bedrijf en de stagaire eventuele

(miscommunicatie)problemen op kunnen lossen en om de vorderingen te bespreken. Tevens vind in

deze periode ook de terugkommiddag op Avans Hogeschool plaats zodat de vordering tussen student

en begeleider kunnen worden besproken.

Subdoel 3: Internationale, Europese en nationale wetgeving en richtlijnen van een offshore substation

bepalen zodat een leidraad voor HFG Engineering kan worden ontwikkeld. Deze dient toegespitst te

worden op de elektrische systemen, instrumentatie, mechanical, piping en structural. (35% van totaal)

20-06 t/m 24-06: Presentatie en verdediging afstudeerproject


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9. Geld

Hier volgt een schatting van wat de projectuitvoering (het ontwerp) zelf gaat kosten. De projectuitvoering

wordt vermeld in uren. Het is van belang dat de student calculeert en inzicht krijgt in de tijdbesteding. De

tariefstelling is hier minder van belang. 28 klokuren staat gelijk aan 1 studiepunt..

Onderdeel Tijd(in klokuren)

Subdoel 1 180

Subdoel 2 300

Tussenverslag & gesprek bedrijfbegeleider 10

Subdoel 3 250

Eindverslag in Nederlands 30

Eindverslag in Engels vertalen 40

Afronding eindverslag, conclusie, logboek, uitloopmogelijkheid. 40

Eindpresentatie maken & voorbereiden 20

Totaal(28uren=1EC) 870

10. Organisatie

Naam van de organisatie: HFG engineering

Bedrijfsbegeleiding: Mendelt Tillema & Frank van der Heijden

Functie: -begeleiden van student in het bedrijf

-bepaald eindresultaat

Onderwijsinstelling: Avans Hogeschool

Hogeschoolbegeleiding: Harry Voermans

Functie: -springt in bij eventuele problemen tussen bedrijf en student

-bepaald eindresultaat

Stagelopende student: Dennis Hermus

Functie: -dient eindrapport op te leveren

-is verantwoordelijk voor het eindresultaat

11. Informatie

Na de eerste 3 weken zal elke periode van 2 weken een logboek worden overhandigd aan de

docentbegeleider. Zo heeft deze inzicht in de vordering van de student. Dit dient via email te worden

voldaan.

Er zal minimaal 1 keer per week een kort vorderingsgesprek plaatsvinden tussen de bedrijfsbegeleider en

de student. Op aanvraag van de begeleider of de student kan dit ook vaker.

Het tussen en eindrapport dienen beide bij het bedrijf en bij de hogeschool te worden ingeleverd. Het

eindrapport dient naast in het Engels te worden opgeleverd. Dit vanwege de internationale marktpositie

van het bedrijf.


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Date: 8/6/2011

Annex 2: standards

Detailed standards

Chapter 3 defines which electronic components and systems the substation platform contains. All these devices

will be tested based on standards before they can be placed in the substation. The standards for these energy

conversion facilities are stricter than the substations on land because the substation is finally placed on sea,

processes very high voltages and run independent. The standards for engineering which are summarized in

chapter 4 are detailed in this annex.

NEN-EN-ISO 9001

NEN-EN-ISO 9001 is an international standard for quality. This standard is not only used in offshore but is a

generally significant meaning in the performance of quality companies. This standard contains the requirements

a company must meet for delivering quality. This does not mean a company or organization actually delivers

quality, but it proves that it can deliver this quality. ISO9001 can be used to assess whether the company /

organization shall be to meet customer requirements, the requirements of the company itself and the laws and

regulations that have been made for that product. Worldwide more than 1 million certificates are issued and most

manufacturing companies have it in possession, including all Heerema Fabrication Group locations.

Summarized the ISO9001 standard contains five checkable requirements which will be checked by audits of an

external company:

1. The management of processes. How will the processes expire and how can they be managed? Are

documents needed? Is it ensured that the right documents for production, service or process are at the

right time at the right place?

2. The responsibility of management. How is responsibility of management regulated? How is the

distribution of tasks, responsibilities and powers? What are the objectives of the company? How

involved is the supervisor in the design and maintenance of the quality?

3. The management of resources. How does the company provide the right resources (such as workplace

equipment, facilities and software) ready in time? How will the training and experience required for

each function provide?

4. The realization of the product. The company understands the requirements of the customer and can also

deliver a product that meets that requirements? How do the company test the product whether the

design meets the requirements? How is the actual production and service process controlled? How

would the work be inspected? Are the products uniquely identifiable and are they carefully handled by

staff? How good are products apart from discarded products?

5. Measuring, analysing and improving of products. How are the customer satisfaction tested? How are

the processes and products requirements check? How would occurred errors resolve that repetition of

the error is prevented? How can that mistakes avoid?


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ISO3834

By using the ISO9001 standard the customer is known that his product meets the requirements, but the ISO9001

do not refer to the requirements of welding. In ISO9001 welding is described as a special process, this is also the

reason most customers asks an ISO3834 certificating. This standard indicates that the company only works with

certified welders, use welding monitoring and that the product meets the legal identification and specifications.

There are three different levels of ISO3834 certificating:

- ISO3834-2: Comprehensive quality. The company belongs to the top of the welding industry. Great en

professional companies, like HFG, haves this certificating.

- ISO3834-3: Standard quality. The company demonstrates to meet the most welding requirements.

- ISO3834-4: Elementary quality. The company controls the fundamentals of welding.

NEN-EN-ISO 14001

NEN-EN-ISO specifies the actual requirements for an environmental management system. It applies to those

environmental aspects which the organization has control and over which it can be expected to have an

influence. This standard can be certified separate, but mostly this will be tested as an part during the NEN-EN-

ISO 9001 audits. Mostly this standard is an part of ISO9001 and contains two important assumptions:

1. Comply with laws, regulations and managing environmental risks. Activities are conducted in an

environmentally conscious way? How do they treat working material properties that are polluting in

nature? Who is responsible for different risks?

2. Striving for constant improvement in environmental performance of the company. Is there a structural

way that cares the environment, so it is minimized contaminated? How and who it is monitored? How

does the company prevent contaminants?

EN-IEC61400

The entire design of wind turbines, substations, etc. is approved in advance by the EN-IEC61400 (Design

requirements wind turbines). This international standard is developed by CENELEC and adopted by the IEC.

The EN-IEC61400 is officially made for wind turbines on land but in 2009 received an addition which the

additional requirements for offshore wind turbines are described. All parts and references to other parts of EN-

IEC61400-3 are therefore applicable to the offshore wind turbines. On the offshore substations, these do partly

apply. The parts of EN-IEC61400 which are most applicable to the offshore substations are described below.

- EN-IEC 61400-1 - Wind turbines part 1: Design requirements wind turbines.

- EN-IEC 61400-3 - Wind turbines part 3: Design requirements for offshore wind turbines

- EN-IEC 61400-12 - Wind turbines part 12: Power performance measurements of electricity producing wind

turbines.

- EN-IEC 61400-13 - Wind turbines part 13: Measurement of mechanical loads.

- EN-IEC 61400-21 - Wind turbines - Part 21: Measurement and assessment of power quality characteristics of

grid connected wind turbines

- EN-IEC 61400-22 - Wind turbines - Part 22: Conformity testing and certification.

- EN-IEC 61400-24 - Wind turbines - Part 24: Lightning protection

- EN-IEC 61400-25 - Wind turbines - Part 25: Communications for monitoring and control of wind power plants

- Overall description of principles and models


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Date: 8/6/2011

DNV-OS-J201

The standard has been prepared for general worldwide application especially for:

— providing an internationally acceptable standard for safe design of offshore substations

— promote a holistic, risk based approach for health and safety of personnel, environmental protection and

safeguarding of the installation considering economic consequences

— serve as a guideline for designers, suppliers, purchasers and regulators.

— define minimum design requirements for installations and supplement these with options for improving

safety

— serve as a contractual reference document between suppliers and purchasers

— specify requirements for offshore installations subject to DNV verification and certification services.

It has been developed primarily to assist in the development of new offshore high voltage AC substations, high

voltage DC substations and associated accommodation platforms. Retrospective application of this standard to

existing installations may not be appropriate. Locally applicable legislation may include requirements in excess

of the provisions in this standard depending on type, size, location and intended service of the installation.

Regional guidance is included throughout this standard by example only.

The standard focuses on fixed, bottom-mounted installations. Taking into account additional requirements, it

may also be applied to floating installations. The principles, requirements and guidance shall be applied to all

stages in the lifecycle of the installation, beginning at the concept design stage. Updates shall be made

throughout the detailed design phase. The principles shall also be applied during the construction, operation and

decommissioning phases and whenever modifications are made.

The standard does not cover oil and gas installations, wind turbines, subsea cables, procedures for construction,

operation or decommissioning of the offshore substations and subsea installations.

IEC EN 60044

Applies to new manufactured current transformers for use with electrical measuring instruments and electrical

protective devices at frequencies from 15 Hz to 100 Hz. Applies basically to transformers with separate

windings, but also to autotransformers.

IEC 60076

Applies to three-phase and single-phase power transformers (including auto-transformers) with the exception of

certain categories of small and special transformers such as:

- single-phase transformers with rated power less than 1 kVA and three-phase transformers less than 5 kVA(IEC

60044)

- Instrument transformers (IEC 61869)

- Transformers for static convectors (IEC 61892)

- Traction transformers mounted on rolling stock (IEC 61287)

- starting transformers (IEC 60947)

- testing transformers (IEC 60044)

- welding transformers (ISO 10656)


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Date: 8/6/2011

Less important electrical standards

IEC EN 60034 Rotating electrical machines (generators).

IEC EN 60044 Instrument transformers.

IEC EN 60137 Insulating bushings for alternating voltages above 1000 V.

IEC EN 60146 Semi-conductor converters.

IEC EN 60439 Low voltage switchgear and control gear assemblies.

IEC EN 61162 Maritime navigation and radio communication equipment and systems -

IEC EN 61174 Operational and performance requirements, methods of testing and

IEC EN 61209 required test results.

IEC EN 61993

IEC EN 61996

IEC EN 62065

IEC EN 61850 Communication networks and systems in substations.

IEC EN 61462 Composite insulators – Hollow insulators for use in outdoor and indoor

electrical equipment – Definitions, test methods, acceptance criteria and

design recommendations.

IEC EN 62155 Hollow pressurized and unpressurized ceramic and glass insulators for use in

electrical equipment with rated voltages greater than 1000 V.

IEC 60840 Power cables with extruded insulation and their accessories for rated voltage

above 30 kV (Um = 36 kV) up to 150 kV (Um = 170 kV) – Test methods

and requirements.

IEC 60947 starting transformers.

IEC 61363 Electrical installations of ships and mobile and fixed offshore units.

IEC 61639 Direct connection between power transformers and gas-insulated metal

enclosed switchgear for rated voltages of 72,5 kV and above.

IEC 61869 Instrument transformers.

IEC 62067 Power cables with extruded insulation and their accessories for rated

voltages above 150 kV (Um = 170 kV) up to 500 kV (Um = 550 kV).

IEC EN 62271 High-voltage switchgear and control gear.

DNV-OS-D202 Automation, Safety and Telecommunication Systems.

NORSOK I-002 Basis Engineering Safety and Automation System Design.

NORSOK Z-010 Electrical, Instrument and Telecommunication Installation.

NORSOK H-003 Heating, ventilation, air conditioning and sanitary systems.

Germ. Loyd IV part 6 Electrical equipment.


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Date: 8/6/2011

Annex 3: Reducing losses by using High Voltage Direct Current(HVDC) The transformer substation can transport the power directly to land or to a convertor station. This convertor

station is situated to transfer HVAC to HVDC and vice versa with using igbt technology, but this technique is

very new. In the early 20th

century it was not possible to increase or decrease direct current (DC) because the

power electronics (like IGBT and thyristor) did not exist, so the voltage from the power station had to be the

same as the voltage for the users. This shortcoming provides high losses over large distances, so the choice for

using alternating current (AC) around the world was relatively simple. But HVAC gives a lot of losses because it

arise reactive power. This power occurs in magnetic fields and very long cables and therefore it has a limited

capacity of several hundred MW possible to transport. The higher the desired power and cable length is the

larger the share reactive power.

Today we have IGBT technology which made it possible to increase or decrease DC. The use of high voltage

directly current (HVDC) has a lot of advantages and is very accurate but the IGBT technology is very expensive.

By using DC at very high power (>100MW), the power losses are smaller compared to high voltage alternating

current (HVAC). HVDC does not arise reactive power because the current direction is constant; but there should

be used two converter stations for HVDC distribution, as shown in Figure A. For short distances it is cheaper to

use HVAC, because HVDC needs two convertor stations (the power distribution on land is still HVAC), but

there is a so-called break-even point where HVAC and HVDC have the same costs.

Figure A: HVDC network

In 2008 a group of four people of IEEE presented a technical and economic analysis to evaluate the benefits and

drawbacks of grid connecting offshore wind farms through a DC link. A first case, concerning a 100MW wind

farm, is thoroughly investigated and cases of larger wind farms (200 and 500 MW) are presented. The main part

of this article was the sensitivity analysis, as shown in figure B. This appears a break-even point of costs for AC

and DC transmission when varying the length of the connection. This break-even point is at a distance of about

90 km from offshore substation to onshore substation, where onshore substation is a few km out of shore. This

break-even-point may fluctuate by commodity prices, by distance between offshore wind farm to shore and from

the distance between shore to onshore substation.

Figure B: break-even point HVDC compared to HVAC offshore (source: IEEE Xplore, 2008)

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