1 © 2015 Eaton. All Rights Reserved.. Suggestion on How to Use Industry Trainers are encouraged to use this material in their sessions Download the presentation file Print the Notes pages and read them as you view the presentation in the “Slide Show” view. In this way you see the slides in large format and have animation (when available)

© 2015 Eaton. All Rights Reserved.. Ground Fault Protection

3 © 2015 Eaton. All Rights Reserved.. Ground Fault Protection All ground faults = short circuits But all short circuits are NOT = ground faults Bolted ground faults (cb or fuse) Low level ground faults = shock/burndown Need for additional protection Therefore ground fault protection

4 © 2015 Eaton. All Rights Reserved.. Ground Fault Protection Ground Fault protection is essential for for safety of personnel and equipment The degree of protection depends upon the device selected. Ground Fault Protection Devices Ground Fault Circuit Interrupter (GFCI) – People Protection Ground Fault Protection of Equipment (GFP) – Equipment Protection

5 © 2015 Eaton. All Rights Reserved.. GFCI Protection NEC Article 100 – GFCI Definition A device intended for the protection of personnel that functions to de-energize a circuit or portion thereof within an established period of time when a current to ground exceeds the values established for a Class A device. Note: Class A ground-fault circuit interrupters trip when the current to ground has a value in the range of 4mA to 6mA.

6 © 2015 Eaton. All Rights Reserved.. GFCI Protection Provides protection against electrical shock and electrocution hazards. Incorporates a current sensing device that monitors the current difference between the ungrounded (hot) and neutral (grounded) conductor.

7 © 2015 Eaton. All Rights Reserved.. 120V Load L N Push-to-Test Sensor ST SS Circ 20A GFCI GFCI Protection GFCI Construction and Operation If the current difference between the hot and neutral conductor exceeds 4-6 mA, the GFCI will trip.

8 © 2015 Eaton. All Rights Reserved.. ST L N SS Circ Sensor 20A GFCI I = V/R I = 120/1000 = 0.12 A R = 1000 OHMS Push-to-Test GFCI Protection Man completes circuit between the line conductor and ground…current does not return through neutral back to source…Sensor picks up leakage current and GFCI trips.. Man Saved.

9 © 2015 Eaton. All Rights Reserved.. ST L N SS Circ Sensor I = V/R = 120/1000 = 0.12 A R = 1000 OHMS 20A GFCI GFCI Protection Man completes circuit between the line conductor and neutral…current in equals current out…Sensor does not pick up leakage current…GFCI does not trip….Man NOT happy!!!

10 © 2015 Eaton. All Rights Reserved.. 20A CB Bathroom Receptacle GFCI protection must be provided per NEC 210.8(A), either by CB or bathroom receptacle GFCI Protection NEC 210.8(A) Dwelling Units Requires ground-fault circuit-interrupter protection for personnel on all 125V, single-phase, 15- and 20-ampere receptacles installed in specified locations Specified locations include bathrooms, garages, outdoors, crawl spaces, unfinished basements, kitchens, wet bar sinks, boathouses, and laundry areas.

11 © 2015 Eaton. All Rights Reserved.. GFP Protection NEC Article 100 – Ground-Fault Protection of Equipment Definition A system intended to provide protection of equipment from damaging line-to-ground fault currents by operating to cause a disconnecting means to open all ungrounded conductors of the faulted circuit. This protection is provided at current levels less than those required to protect conductors from damage through the operation of a supply circuit overcurrent device.

12 © 2015 Eaton. All Rights Reserved.. GFP Protection – Why? Rat causes phase to ground fault I = V/R I = 277/0.1 I = 2,770A 3000A CB will not trip! B A C N 277V 480V R = 0.1 OHMS 3,000A CB

13 © 2015 Eaton. All Rights Reserved.. Ground Fault Protection Requires ground-fault protection for each solidly grounded wye service disconnect where: System voltage is more than 150V to ground, but not exceeding 600V phase to phase Rated 1000A or more Maximum ground-fault current setting – 1200A Maximum ground-fault time-delay setting – 1 second for ground fault currents equal to or greater than 3,000A.

14 © 2015 Eaton. All Rights Reserved.. Ground Fault Protection Ground Fault Protection is not required: For fire pumps (not permitted) or continuous process industrials where a non-orderly shutdown would result in additional hazards. 240V/120 single phase or 240V three phase systems. Services (or feeders) above 600V. Service with six disconnects or less where each disconnect is less than 1000 amperes. A 4000 ampere service split into ampere switches would not require GFP. Delta, ungrounded, or resistance/impedance grounded systems.

15 © 2015 Eaton. All Rights Reserved.. Ground Fault Protection Ground Fault Protection is required on feeder disconnect switches, in accordance with , where: System voltage is more than 150V to ground, but not exceeding 600V phase to phase Rated 1000A or more Exceptions: Fire pumps or continuous process industrials where a non- orderly shutdown would result in additional hazards. If ground-fault protection is provided on the supply side of feeder.

16 © 2015 Eaton. All Rights Reserved.. Ground Fault Protection Ground fault protection as required by

17 © 2015 Eaton. All Rights Reserved.. Ground Fault Protection GFP not required on feeder equipment when it is provided on the supply side of the feeder (except as required for Health Care Facilities per Article 517)

18 © 2015 Eaton. All Rights Reserved.. Ground Fault Protection Equipment ground fault protection, in accordance with , is required for each disconnect rated 1000A or more, for 480/277V systems, that will serve as a main disconnect for a separate building or structure.

19 © 2015 Eaton. All Rights Reserved.. GFP Protection GFP Can Sense low magnitude ground faults Protect equipment against low magnitude ground fault GFP CANNOT Protect people or prevent ground faults and electric shock Protect against 3 phase, phase-phase or phase-neutral faults Protect against high level ground faults Guarantee selective coordination – may adversely affect selective coordination

20 © 2015 Eaton. All Rights Reserved.. Ground Fault Protection Types of GFPs GFEP (Earth Leakage) Zero Sequence Residual (Neutral Ground Strap)

21 © 2015 Eaton. All Rights Reserved.. Earth Leakage (GFEP) Earth Leakage (GFEP – Ground Fault Equipment Protector) circuit breakers detect ground faults of 30 mA or more. Typically Rated 277V, 100A or less 277V Load L N Push-to-Test Sensor ST SS Circ 20A GFEP

22 © 2015 Eaton. All Rights Reserved.. Zero Sequence GFP CT encloses phase and neutral conductors 1 CT as shown or 4 CTs (one for each phase and neutral) CTs Sense current difference Signals GF Relay ST Opens Disconnect Typically available on CB & Fused Switches rated 400A or more. B A C N 277V 480V GF Relay ST 3000A BPS

23 © 2015 Eaton. All Rights Reserved.. Zero Sequence GFP - Operation B A C N 277V 480V GF Relay ST 3000A BPS Current does not return through neutral/CT If current to ground exceeds setting on GF Relay, BPS will shunt trip.

24 © 2015 Eaton. All Rights Reserved.. Residual GFP B A C N 277V 480V GF Relay ST 3000A BPS Grounding Strap

25 © 2015 Eaton. All Rights Reserved.. Residual GFP - Operation B A C N 277V 480V GF Relay ST 3000A S/F Current does not return through neutral Residual CT senses current If current through grounding strap exceeds setting on GF Relay, BPS will shunt trip.

26 © 2015 Eaton. All Rights Reserved.. Calculating Ground Fault Energy kW-Cycles can be used to determine amount of damage based upon ground fault energy. kW-Cycles = (I X E X t)/1000 I = Ground fault current E = 100V of 277/480V system t = Arcing time in cycles

27 © 2015 Eaton. All Rights Reserved.. GFP Protection: kW-Cycles Equipment Damage from ground-faults can be measured by kW-Cycles 100 kW-Cycles – Spit marks on Equipment 2000 kW-Cycles – Limited damage. Equipment can be put back in operation after cleaning smoked and spotted areas and repairing insulation if necessary 10,000 kW-Cycles – Serious damage. Usually will not burn through. Equipment will probably need parts replaced, such as bus bars.

28 © 2015 Eaton. All Rights Reserved.. GFP Protection: kW-Cycles 20,000 kW-Cycles – Serious damage. Fault will probably burn through and spread to other sections of equipment. Equipment will need extensive repairs and/or replacement. Over 20,000 kW-Cycles – Much destruction of equipment…fire. Equipment will need extensive repairs and/or replacement.

29 © 2015 Eaton. All Rights Reserved.. kW-Cycles vs. Fault Current Protective device selected can determine degree of protection as shown in chart.

30 © 2015 Eaton. All Rights Reserved.. GFP Considerations – Current Limitation This system offers: 1. Some degree of arcing and low magnitude ground fault protection by the ground fault relay operating the switch. 2. Current-limitation for high magnitude ground faults and short-circuits by current-limiting fuses, which provides component protection for the switchgear. This system offers: 1. Some degree of arcing and low magnitude ground fault protection by the ground fault relay operating the circuit breaker. Note: This system does not provide current- limitation for high magnitude ground faults and short-circuits.

31 © 2015 Eaton. All Rights Reserved.. GFP Considerations - Coordination A ground fault on a feeder or branch circuit can cause the main device to open.

32 © 2015 Eaton. All Rights Reserved.. GFP Considerations - Coordination The system on the left has a lack of selective coordination – the short- circuit on the branch device causes the main to open and results in a black-out situation. The system on the right has selective coordination - only the device nearest the short circuit opens.

33 © 2015 Eaton. All Rights Reserved.. GFP Relay & OCPD Curves Effective time current curve for line to ground fault with 1600 ampere fuse and ground fault protection set at 1200 amperes (switch clearing time of 4 cycles).

34 © 2015 Eaton. All Rights Reserved.. GFP Relay & OCPD Curves Effective time current curve for line to ground fault with 1600 ampere circuit breaker and ground fault sensor setting at 1200 amperes.

35 © 2015 Eaton. All Rights Reserved.. GFP Considerations - Coordination Low Magnitude Ground Fault Longer ground fault relay delay permits larger feeder fuse to coordinate with main relay. High Magnitude Ground Fault Fuses are selectively coordinated.

36 © 2015 Eaton. All Rights Reserved.. GFP Considerations - Coordination Low Magnitude Ground Fault A lack of coordination exists for ground faults between 1200 amperes and 1800 amperes. High Magnitude Ground Fault Faults greater than 11,000A will cause the 200A and 1200A Power CB to open. Adding STD to the 1200 amp Power CB would allow the two CBs to selectively coordinate.

37 © 2015 Eaton. All Rights Reserved.. Ground Fault Protection If the service or feeder is equipped with ground fault protection in accordance with or , the next level of feeders is also required to have ground fault protection. Separation between the service and feeder ground fault relays must achieve total selective coordination.

38 © 2015 Eaton. All Rights Reserved.. Ground Fault Protection Service Disconnect is equipped with ground fault protection per Feeders are equipped with ground fault protection and have manufacturer recommended separation between the two ground fault curves. Complies with NEC

39 © 2015 Eaton. All Rights Reserved.. Ground Fault Protection Main A Fuse Feeder A Fuse GFP on Main & Feeder Meets

40 © 2015 Eaton. All Rights Reserved..