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The Power in

Electrical Safety

NEHES – August 17, 2018 Twin State Seminar

Isolated Power Systems in Healthcare Facilities

Presenter: David Knecht – Bender Inc.

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Agenda

Why Electrical Safety in Hospitals

Technical Overview of Isolated Power Systems

Codes & Standards

Best Practice (Equipment Selection, Design, Installation, Maintenance)

FAQs- What should I do when the LIM goes into alarm?

- What preventive & periodic maintenance is required for the LIM?

- When should the Isolated Power System integrity be tested?

- What is the maximum conductor length for an Isolated Power Panel?

- How many circuits (breakers) can I have in an Isolated Power Panel?

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10

Why Electrical Safety in Healthcare Facilities?

Key types of risk

Risk due to electric current

Mechanical risk sources

Chemical risk sources

Thermal risk sources

Risk due to ionising radiation

Risk due to RF fields

Biological hazards

Human failure

Risk to life and property

Dangerous currents flowing through the body

Interruption of power supply

Inadequate quality supply voltage

Excessive temperatures

Arcing

Ignition of explosive mixtures

Extraneous influences, cumulative effects

12BENDER > Presentation Theme

Why Electrical Safety in Healthcare Facilities?

The risks for the patients in hospitals ...

The patient`s natural reactions to hazards are often reduced or switched-off

The heart muscle is highly sensitive to electric currents (currents > 10 µA)

The insertion of catheters and invasive devices bypasses the electrical

resistance of the skin

Body functions are temporarily or continuously supported by multiple

medical electrical devices

Fire risks through the use of anaesthetics, disinfectants or cleaning agents

14BENDER > Presentation Theme 14

First (Tolerable) Failure” principle

“First (Tolerable) Failure” principle

- Failures can occur but they must not lead to a risk

- Dual protection is provided

- The First Failure must be detected and eliminated before a second failure occurs

- Control of the “First Failure” in a reasonable safe system


Why Electrical Safety…


Isolated Power Systems

Overview

To provide ungrounded single-phase power to patient care areas deemed as “Wet Procedure Locations”, so as to:

Reduce electric shock hazard

- Limits magnitude of ground fault current

- Practically eliminate danger of massive electrical shocks (macro shock) from ground fault

Increase operational safety

- Increased electric power reliability by not interrupting power on ground fault

Eliminate arcing on ground faults



Grounded vs. Isolated (Ungrounded) System



Leakage Current

All energized electrical components – cables, windings, medical devices – have a distributed capacitance to ground – called leakage capacitance

Cable insulation also has distributed conductance to ground

- because insulation resistance is not infinite

- modeled as a parallel impedance to ground

Sum of capacitive and resistive current to ground known as Leakage Current

Contributing factors resulting in increased Leakage Current

- proximity of grounded & ungrounded components

- length of ungrounded conductors

- quantity of devices connected to the system

- devices containing ground filtration circuitry



Electric Shock Hazard

Leakage Current Grounded System

A high fault current can flow

The fault current is only limited by the body

impedance (1kΩ)

IF =Supply Voltage

(𝑍𝐵+𝑍𝐹)→

120𝑉

(1𝑘Ω + 0Ω)= 𝟏𝟐𝟎𝒎𝑨

Leakage Current Isolated Power System (IPS)

The IPS is a “small” local network with low

leakage capacitances

The fault current is limited by:

ZB = body impedance

ZCe = impedance of the fault loop

ICe =Supply Voltage

(𝑍𝐵+𝑍𝑐𝑒)→

120𝑉

(1𝑘Ω + 500𝑘Ω)= 𝟎. 𝟐𝟒𝒎𝑨

Zce = 500 kΩZB = 1 kΩ

120V

ZB = 1 kΩ

ZF = 0Ω

120V



Operational Safety

Fault Grounded System

A fault current flows determined by the ground

impedance and the fault.

IF < IK (IK typically = 20A)

Overcurrent Protection Device does not trip

Risk of equipment malfunctions

IF ≥ IK Overcurrent Protection Device trips

Unexpected interruption of power

Fault Isolated Power System (IPS)

In the event of a fault RF only a very low current

ICe flows

Overcurrent Protection Device does not trip

In the event of single conductor to ground fault,

power is not interrupted

Alarm indicated by a Line Isolation Monitor



Line Isolation Monitor (LIM)


- test instrument designed to measures how “isolated” the system is from ground

- by continually measuring impedance to ground of each phase

Predicts and displays what the highest ground fault current would be if the line with the highest impedance would be connected to ground

This predicted current is called the Total Hazard Current

- Total Hazard Current alarm point 5 mA (NFPA 99 & NEC)




When a ground fault occurs the LIM will:

- sense the new lower impedance to ground

- re-calculate the fault current that would flow if the remaining phase (with the highest impedance to ground) were to become grounded

LIM predicts the highest fault current for the next ground fault to occur (definition of hazard current)

- display a hazard message and generate an audible alarm

LIM issues a hazard alarm when either:

- the leakage current becomes excessive

- a fault occurs between either conductor and ground



Summary

Electrical Shock

- Added protection against electrical shock hazards resulting from the system’s high impedance to ground (capacitive/resistive) return path

Continuity of Supply

- Power will remain during a single fault condition (i.e. L1 or L2 connected to Ground)

Advanced Warning of Faulty Equipment

- Provides a warning when the insulation integrity of medical devices connected to the Isolated Power System are compromised


Codes & Standards

Overview

Applicable Codes

- NFPA 99:2012 - Health Care Facilities Code

minimum requirements for the performance of various system

- NFPA 70:2014 - National Electrical Code, Article 517

minimum requirements for the installation of various electrical system

Always check with your local Authority Having Jurisdiction (AHJ).

- Local codes such as North Carolina Department of Health and Human Services (NCDHHS) and Agency for Health Care Administration (AHCA) have more stringent requirements for the installation & performance of Isolated Power Systems.

CMS approved into Federal Law in 2016

Plans submitted after 7/5/2016 must comply with NFPA 99:2012


Codes & Standards

NFPA 99 - 2012 Edition

Chapter 4 - Fundamentals

- 4.1 Building System Categories

- 4.2 Risk Assessment

- 4.3 Application

Chapter 6 - Electrical Systems

- 6.1 Applicability

- 6.2 Nature of Hazards

- 6.3 Electrical System

- 6.4 Essential Electrical System Requirements —Type 1




46

Codes & Standards

Risk Categories - Patient Care Spaces

Category 1Critical Care Space

Failure of system or equipment is likely to cause major injury or death to patients or caregivers.

Examples:• Operating rooms• Cardio Cath. labs• Delivery Rooms• Intensive Care Units• Post-anesthesia units• Trauma rooms

Category 2General Care Space

Failure of system or equipment is likely to cause minor injury to patients or caregivers.

Examples:• Inpatient bedrooms• Dialysis rooms• In-vitro rooms• Procedural rooms

Category 3Basic Care Space

Failure of system or equipment is not likely to cause injury to patients or caregivers, but can cause discomfort.

Examples:• Examination space • Medical & Dental offices • Nursing homes• Limited care facilities

Category 4Support Space

Failure of system or equipment has no impact on patients or caregivers.

Examples:• Anesthesia work rooms• Laboratories• Morgues• Waiting rooms• Utility rooms• Lounges

4.1* Building System Categories


Codes & Standards

NFPA 99 - 2012 Edition

Chapter 4 - Fundamentals

- 4.1 Building System Categories

- 4.2 Risk Assessment

- 4.3 Application


- 6.1 Applicability

- 6.2 Nature of Hazards

- 6.3 Electrical System





6.3 Electrical System

Codes & Standards


6.3.1 Sources6.3.2 Distribution

6.3.2.2* All Patient Care Rooms6.3.2.2.1 Regular Voltage Wiring Requirements6.3.2.2.2 Grounding Requirements6.3.2.2.3* Grounding Interconnects6.3.2.2.4 Protection Against Ground Faults6.3.2.2.5 Low-Voltage Wiring6.3.2.2.6 Receptacles6.3.2.2.7 Special Grounding6.3.2.2.8 Wet Procedure Locations6.3.2.2.9 Isolated Power6.3.2.2.10 Essential Electrical Systems (EES)6.3.2.2.11 Battery-Powered Lighting Units

6.3.2.3 Laboratories6.3.2.4 Other Non-patient Areas6.3.2.5 Ground-Fault Protection6.3.2.6 Isolated Power Systems

6.3.3 Performance Criteria and Testing6.3.3.1 Grounding Systems in Patient Care Rooms

6.3.3.1.1* Grounding System Testing6.3.3.1.2 Reference Point6.3.3.1.3* Voltage Measurements6.3.3.1.4* Impedance Measurements6.3.3.1.5 Test Equipment6.3.3.1.6 Criteria for Acceptability for New Construction

6.3.3.2 Receptacle Testing in Patient Care Rooms6.3.3.3 Isolated Power Systems6.3.3.4 Ground-Fault Protection Testing

6.3.4* Administration of Electrical Systems6.3.4.1 Maintenance and Testing of Electrical System

6.3.4.2.1* General6.3.4.2 Record Keeping

6.3.4.2.2 Isolated Power System (Where Installed)


Codes & Standards

NFPA 99 - Wet Procedure Locations

Wet Procedure Locations- area in a patient care room where a procedure is performed

- normally subject to wet conditions while patients are present

- including standing fluids on the floor or drenching of the work area

- either of which condition is intimate to the patient or staff

Wet procedure locations shall be provided with special protection against electric shock.

- Isolated Power System or Class A GFCI Receptacles

- GFCI only if loss of power can be tolerated

Operating rooms shall be considered to be a wet procedure location, unless a risk assessment conducted by the health care governing body determines otherwise.

- risk assessment should include all relevant parties

clinicians, biomedical engineering staff, and facility safety engineering staff

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Codes & Standards

CMS Survey

Centers for Medicare and Medicaid Services K-Tags

K913

K914


Codes & Standards

NFPA 99 – Risk Classifications (cont.)

Classification ... with medical staff ... and circumstance

Classification of the risk should be

made in agreement with:

medical staff (clinicians, biomedical

engineering, and facility safety

engineering)

designer of record

authority having jurisdiction

Governing Body of the facility

- indicate medical procedures that

will be performed in the space

- determine equipment and contact

between applied parts and the

patient

- Can procedures be discontinued at

any time & repeated?

- Can the patient be expected to

accept an interruption?

- Is the patient’s natural resistance

(skin) bypassed?

- Are only listed electrical medical

devices connected to the supply?


Best Practices

Equipment Selection

Space usage - medical equipment & device list

- Load & impedance determinations

Recommended to limit 120V systems to 10kVA or less

- Supply needs for equipment operating >120V (i.e. portable lasers)

Physical location

- Panel location - In-room or adjacent to room

Install centrally as close to loads as possible

Indication must be installed in locations where circuits are supplied from the Isolated Power System

Isolated Power Systems supplying 120V circuits can only supply one Operating Room

- Wall structure - depth & load bearing capability

Most systems 8”+ deep & 24” wide

Can weigh up to 600lbs

- Accessibility of system

Isolated Power Panels – Types

71

IP - Operating Room

- most common

- 3, 5, 7½, 10 kVA

- 6” or 8” deep

- 43” tall x 24” wide

- Up to 16 circuits (SQD, Eaton, GE)

recommended not to exceed 12

IP - ICU

- Like above except:

includes receptacles and/or ground jacks on front panel

48” tall x 24” wide


IX – Dual (Duplex) System Panel

- Two systems in a common enclosure

- Requires independent feeder per system

- 3, 5, 7½, 10 kVA

- 8” deep


- Up to 16 circuits per system (SQD, Eaton, GE)



ID – Dual Output Voltage Panel

- provides both 120V and 208V (220V, 230V or 240V) power

- single feeder

- 10, 15, 20, 25kVA

- 12” or 14” deep


- 56”x34” available includes receptacles and/or

ground jacks on front panel

- Up to 16 circuits (SQD, Eaton, GE)



IP – Controlled Power Panel

- provides multiple ORs with 208V (220V, 230V or 240V) power

- 15 or 25kVA

- Up to 12 circuits

- maximum of 6 circuits simultaneously active


- PLC limits the number of simultaneously “active” circuits

- circuit selection is operated via laser receptacle module (door contact) located in OR

XRM – Laser Receptacle Module

- Receptacle, Remote Indicator,

& PLC input (door) contact

- Optional “IN-USE” indicator

MK Series

LED display for long life

Mounts to standard electrical box

Includes “Mute” button

Optional:

- “Push to Test” Button

- Transformer Overload Indication

- Numeric THC / Transformer Load Value

Easy to clean rugged stainless steel and Lexan front foil design

Remote Indicating Devices

MK800MK2430

Isolated Power System - Basic

Isolated Power System - Options

Mains load monitoring



Branch circuit ground fault location



Branch circuit load monitoring

Branch circuit ground fault location


Best Practices

Design

Overcurrent Protection & Switches

- Branch over current protection devices (OCPD) shall be 2-pole, since both conductors are current carrying

- Hardwired fixed equipment should be connected with 2-pole switches

boom brake & motor, film viewers, etc.

Isolated Conductors

- Dielectric constant of 3.5 or less is recommended (XHHW, XHHW-2)

- Identification of conductors; insulation shall be:

Orange with a distinctive colored stripe other than white, green, or gray

Terminated on Receptacle “Neutral” terminal

Brown with a distinctive colored stripe other than white, green, or gray

Terminated on Receptacle “HOT” terminal

- Keep length of conductors to a minimum.

Longer runs = higher leakage


Best Practices

Design

Conduit

- Install “as a crow flies” or “beeline”

- Use nonflexible metal conduit

- ¾" conduit minimum - not more the 2 circuits (6-conductors) per ¾" conduit.

- Use 1" conduit with 3 or 4 circuits, but do not use larger than 1”.

Devices per Circuit

- Recommended to limit circuits to two duplex receptacles (4 outlets)

The LIM is looking for a worse case scenario.

Adding receptacles to a circuit for additional equipment will result in additional leakage


Best Practices

Design

Use “Hospital Grade” devices only

- Do not use GFCI, Surge Protection Devices, Relocatable Power Taps with Ground checks, or Isolated Ground devices

Any device that has a relationship with an equipment ground to function properly, will not operate properly on an IPS

Equipment located outside the patient vicinity not typically connected to IPS

- Fixed-mounted, permanently connected therapeutic equipment not likely to become energized with non-moveable elements

- Field Lighting (overhead ceiling lights)

- Dedicated receptacle for room cleaning equipment


Frequently Asked Questions

What should I do when the LIM goes into alarm?

What preventive & periodic maintenance is required for the LIM?

When should the Isolated Power System integrity be tested?

What is the recommended maximum conductor length for an Isolated Power Panel?

How many circuits (breakers) can I have in an Isolated Power Panel?



Operational Questions

(Q): What should I do when the LIM goes into alarm?

Do NOT endanger the patient by discontinuing the procedure prematurely

- The alarm does not mean there is imminent danger

Acknowledge the alarm & immediately notify personnel responsible for the equipment’s maintenance

If the alarm happened soon after an electrical equipment was connected, disconnect the equipment that was most recently connected

- Only disconnect the equipment if it will not endanger the patient.

Once the procedure is complete, responsible personnel should investigate & correct the alarm’s root cause.

- This process is often tedious and time consuming (if done manually) and requires de-energizing the circuits on the system.

- Automatic on-line fault location systems (EDS / FLS) are available in the marketplace.




(Q): What preventive & periodic maintenance is required for the LIM?

LIM Testing

- External Fault Impedance / Response Test

after installation, and prior to being placed in service and/or any repair or renovation to the electrical distribution system

all LIM manufactures recommend minimum of annual testing

- Functional - Audible & Visual Alarm Test

performed by depressing test button on unit

annually for digital LIMs & monthly for analog LIMs




(Q): When should the Isolated Power System integrity be tested?

IPS system

- after installation, and prior to being placed in service and/or any repair or renovation to the electrical distribution system

Lug and breaker torque validation (annual)

Grounding system integrity (recommended every 1 – 3 years) System impedance & hazard current (recommended every 1 – 3 years)



Design Questions

(Q): What is the maximum conductor length for an Isolated Power Panel?



Design Questions




Design Questions


Minimum NFPA acceptance criteria for impedance to ground is 200 kΩ

On 120V system, the maximum allowable system hazard current is calculated as follows:

- 𝐼 𝑡𝑜𝑡𝑎𝑙 =𝑉

𝑍=

120 𝑉

200 𝑘Ω= 600 𝑢𝐴

Manufacture’s permissible leakage (𝐼𝑚) for the IPS according to UL-1047 (table 30.1 & 30.2):

- 𝐼 𝑚 = 𝐼 𝑖𝑛𝑡𝑒𝑟𝑖𝑜𝑟 + 𝐼 𝑡𝑟𝑎𝑛𝑠𝑓𝑜𝑟𝑚𝑒𝑟 → 50 𝑢𝐴 + 25 𝑢𝐴 = 75 𝑢𝐴

Leakage current of XLPE cable (𝐼𝑤) is 1 μA/ft in metallic conduit, as per IEEE 602-2007

- Recommend conservative value of 1.1 μA/ft. to allow for manufacture variations

Therefore, the recommended conductor length (𝑊𝑚𝑎𝑥) can be calculated as follows:

- 𝑊𝑚𝑎𝑥 = 𝐼𝑡𝑜𝑡𝑎𝑙 − 𝐼𝑚 ÷ 𝐼𝑤 → 600𝑢𝐴 − 75𝑢𝐴 ÷ 1.1𝑢𝐴 ≅ 480𝑓𝑡

(A): The recommended conductor length of XLPE wire is 480ft.



Design Questions

(Q): How many circuits (breakers) can I have in an Isolated Power Panel?

UL-1047 limits the quantity of branch breakers per system to 16 maximum.

Recommended maximum conductor length per system (𝑊𝑚𝑎𝑥) is calculated as ~480ft

Most modern general purpose operating rooms are >600sqft with >10ft ceilings.

- Based on standard design practices, the average linear length per circuit (𝑊𝑛), originating from a centrally located IPS is ~40-58ft.

Thus the recommended number of circuits can be calculated as:

- 𝐶𝑚𝑎𝑥 =𝑊

𝑚𝑎𝑥

𝑊𝑛

=480 𝑓𝑡

40 𝑓𝑡= 12

- 𝐶𝑚𝑎𝑥 =𝑊

𝑚𝑎𝑥

𝑊𝑛

=480 𝑓𝑡

58 𝑓𝑡= 8

(A): The recommended number of breakers is 8 – 12 per system.


Why Electrical Safety…

Our families deserve at least the same level of electrical shock protection in

critical healthcare environments as is provided for them in residential washbasin

locations.

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