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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
15BENDER > Presentation Theme 15
Why Electrical Safety…
16BENDER > Presentation Theme
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
17BENDER > Presentation Theme 17
Isolated Power Systems
Grounded vs. Isolated (Ungrounded) System
18BENDER > Presentation Theme 18
Isolated Power Systems
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
24BENDER > Presentation Theme 24
Isolated Power Systems
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
25BENDER > Presentation Theme 25
Isolated Power Systems
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
26BENDER > Presentation Theme 26
Isolated Power Systems
Line Isolation Monitor (LIM)
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)
27BENDER > Presentation Theme 27
Isolated Power Systems
Line Isolation Monitor (LIM)
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
28BENDER > Presentation Theme
Isolated Power Systems
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
36BENDER > Presentation Theme 36
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
39BENDER > Presentation Theme 39
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
- 6.5 Essential Electrical System Requirements —Type 2
- 6.6 Essential Electrical System Requirements —Type 3
46BENDER > Presentation Theme 46
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
48BENDER > Presentation Theme 48
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
- 6.5 Essential Electrical System Requirements —Type 2
- 6.6 Essential Electrical System Requirements —Type 3
49BENDER > Presentation Theme 49
6.3 Electrical System
Codes & Standards
Chapter 6 - Electrical Systems
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)
58BENDER > Presentation Theme
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
https://hubbellcdn.com/brochure/Premise_WLBVM007.pdf
59BENDER > Presentation Theme 59
Codes & Standards
CMS Survey
Centers for Medicare and Medicaid Services K-Tags
K913
K914
62BENDER > Presentation Theme
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?
69BENDER > Presentation Theme
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
Isolated Power Panels – Types
IX – Dual (Duplex) System Panel
- Two systems in a common enclosure
- Requires independent feeder per system
- 3, 5, 7½, 10 kVA
- 8” deep
- 71” tall x 34” wide
- Up to 16 circuits per system (SQD, Eaton, GE)
recommended not to exceed 12
Isolated Power Panels – Types
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
- 51” tall x 34” wide
- 56”x34” available includes receptacles and/or
ground jacks on front panel
- Up to 16 circuits (SQD, Eaton, GE)
recommended not to exceed 12
Isolated Power Panels – Types
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
recommended not to exceed 4
- 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
Isolated Power System - Options
Mains load monitoring
Branch circuit ground fault location
Isolated Power System - Options
Mains load monitoring
Branch circuit load monitoring
Branch circuit ground fault location
81BENDER > Presentation Theme
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
82BENDER > Presentation Theme
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
83BENDER > Presentation Theme
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
85BENDER > Presentation Theme
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?
86BENDER > Presentation Theme
Frequently Asked Questions
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.
87BENDER > Presentation Theme
Frequently Asked Questions
Operational Questions
(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
88BENDER > Presentation Theme
Frequently Asked Questions
Operational Questions
(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)
89BENDER > Presentation Theme 89
Frequently Asked Questions
Design Questions
(Q): What is the maximum conductor length for an Isolated Power Panel?
90BENDER > Presentation Theme 90
Frequently Asked Questions
Design Questions
(Q): What is the maximum conductor length for an Isolated Power Panel?
91BENDER > Presentation Theme
Frequently Asked Questions
Design Questions
(Q): What is the maximum conductor length for an Isolated Power Panel?
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.
92BENDER > Presentation Theme
Frequently Asked Questions
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.
93BENDER > Presentation Theme 93
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.