Ground Fault Relays and Sensors (GFP, BGFL, GFM)
There are many different applications for and methods of using the Electromagnetic Industries products and we cannot be familiar with every particular system configuration that each of our products may be used in. For this reason we may not be able to give direct advice of how to set up your particular system. Any statements here are general statements that may or may not apply directly to your specific system configuration. We can only speak to how the Electromagnetic Industries components and products are designed to operate. Any questions concerning your complete system configuration or proper application of our products in your particular system must be addressed by your switchgear manufacturer and/or your EE.
Question: What do I set my "Pick Up Amps" and "Time Delay" setting to?
Answer: These set-points are determined by the level of protection required. Any questions concerning your particular system configuration or proper settings for your application must be addressed by your switchgear manufacturer and/or your EE.
What I can tell you is that:
Although It has been our observation, most applications do set the relay at less than its maximum setpoints, we “Electromagnetic Industries” cannot determine what those setpoints should be.
Obviously, the lower the setpoints, the more protection you have against ground fault. The trade off is that if you are having insulation breakdown, or an inadvertent short to ground, the relay may react quicker than your power distribution panel breakers and trip the entire system rather than just the breaker in the panel feeding the piece of equipment.
What I can tell you is that:
- UL 1053 allows up to 2 Sec. Max. time delay up to 150% of Pickup setting or 1 Sec. Max. time delay above 250% of Pickup setting and to have max setpoints to be 1200A
- NEC Section 230 allows the maximum setting of the ground fault protection to be 1200A and the maximum time delay is 1 sec. for ground faults equal to or greater than 3000A
Although It has been our observation, most applications do set the relay at less than its maximum setpoints, we “Electromagnetic Industries” cannot determine what those setpoints should be.
Obviously, the lower the setpoints, the more protection you have against ground fault. The trade off is that if you are having insulation breakdown, or an inadvertent short to ground, the relay may react quicker than your power distribution panel breakers and trip the entire system rather than just the breaker in the panel feeding the piece of equipment.
Question: How do I install the line conductors through the sensor?
Answer: The Ground Fault Relay and associated Sensors are used together to provide protection from a ground fault condition. The sensor is a Zero Sequence sensor that uses phase summation to determine if there is a ground fault condition. (i.e. The total of the phase angle and amplitude of power flowing from and returning to the source should be zero)
For three phase systems where there is a Neutral present, all three phases and the Neutral MUST go through the sensor for proper operation and detection of ground faults. Failure to have the Neutral go through the sensor, or not properly wiring the Neutral may result in nuisance trips and possibly failure for the relay to work in the event of a ground fault.
For three phase systems without a neutral and with an “Equipment Ground”, the ground wire must NOT go through the window. Putting the Ground wire through the window may prevent the relay from taking action if there is a ground fault present. With the ground not going through the window, if there is any current going to ground the GFP and Sensor WILL interoperate it as a Ground Fault condition.
For three phase systems where there is a Neutral present, all three phases and the Neutral MUST go through the sensor for proper operation and detection of ground faults. Failure to have the Neutral go through the sensor, or not properly wiring the Neutral may result in nuisance trips and possibly failure for the relay to work in the event of a ground fault.
For three phase systems without a neutral and with an “Equipment Ground”, the ground wire must NOT go through the window. Putting the Ground wire through the window may prevent the relay from taking action if there is a ground fault present. With the ground not going through the window, if there is any current going to ground the GFP and Sensor WILL interoperate it as a Ground Fault condition.
Question: What is a Zero Sequence Sensor?
Answer: Zero Sequence sensors are used for detecting a ground fault by measure residual current, which is the product of the vector summation of the three phases when brought through a single sensing window. This method is based on the concept that the total of the phase angle and amplitude of power flowing from and returning to the source equals zero. We believe the Zero Sequence method is the best method due to it being the most sensitive to Ground Faults and it has an inherent noise immunity. It is also important to note that the sensor cannot generate a signal unless a fault condition occurs. This in itself prevents nuisance trips.
Question: What are the advantages of Ground Fault Relays over using fuses?
Answer: There are many advantages of Ground Fault Relay (GFR) over just fuses:
1) A GFR can be quickly reset once the fault is corrected or for trouble shooting purposes.
2) The GFR can be set for different time delays and amperage levels. (It is important to note that these set points selection are no more or less critical than selection of the proper fuse for the same application.)
3) The GFR can be adjusted and/or reset without having to "Lock Out/Tag Out" or suiting up to open the panel.
4) With a GFR, there is no need to keep additional parts in inventory or rush replacements if there is a trip.
5) Some of our models have Inverse Time Curves for added protection.
6) Some of our models have Zone Interlocks to isolate a Ground Fault to only the panel/switchgear effected.
7) Some of our models have Fault Indications even before the unit reaches its GF set-points allowing for troubleshooting before a trip occurs.
8) Some of our models have the ability to indicate GF Level even after the trip (power down)
9) Most of our GF Relays have "Push to Test" allowing the system to be tested at any time.
10) Most of our GF Relays have a "Shunt Trip Bypass" that also allows for testing of the relay and sensor without tripping the Shunt Trip Coil.
1) A GFR can be quickly reset once the fault is corrected or for trouble shooting purposes.
2) The GFR can be set for different time delays and amperage levels. (It is important to note that these set points selection are no more or less critical than selection of the proper fuse for the same application.)
3) The GFR can be adjusted and/or reset without having to "Lock Out/Tag Out" or suiting up to open the panel.
4) With a GFR, there is no need to keep additional parts in inventory or rush replacements if there is a trip.
5) Some of our models have Inverse Time Curves for added protection.
6) Some of our models have Zone Interlocks to isolate a Ground Fault to only the panel/switchgear effected.
7) Some of our models have Fault Indications even before the unit reaches its GF set-points allowing for troubleshooting before a trip occurs.
8) Some of our models have the ability to indicate GF Level even after the trip (power down)
9) Most of our GF Relays have "Push to Test" allowing the system to be tested at any time.
10) Most of our GF Relays have a "Shunt Trip Bypass" that also allows for testing of the relay and sensor without tripping the Shunt Trip Coil.
Question: Please explain the Ground Fault Relays Time Delay Curves.
Answer: For the Model BGFL and Model GFP units with the standard (No Inverse Curve) the fault condition must be present for the full time delay for the unit to trip. The level of the ground fault above the set-point does not affect the duration of the time delay (i.e. the time delay is the same at 100% as it is at 500% of trip set-point)
The Model BGFL does not have Inverse Time Capability.
For the Model GFP with Linear Curve, every time the amperage doubles (above the set-point) the time delay is reduced by 50%. (i.e. Set point of 500A and a time delay of 1 Sec, at 500A the delay is 1 sec. and at 1000A the delay would be .50 sec.)
For the Model GFP with Logarithmic Curve, every time the amperage doubles (above the set-point) the time delay is reduced by 75%. (i.e. Set point of 500A and a time delay of 1 Sec, at 500A the delay is 1 sec. and at 1000A the delay would be .25 sec.)
Please refer to the product Data Sheets for the time delay curves.
The Model BGFL does not have Inverse Time Capability.
For the Model GFP with Linear Curve, every time the amperage doubles (above the set-point) the time delay is reduced by 50%. (i.e. Set point of 500A and a time delay of 1 Sec, at 500A the delay is 1 sec. and at 1000A the delay would be .50 sec.)
For the Model GFP with Logarithmic Curve, every time the amperage doubles (above the set-point) the time delay is reduced by 75%. (i.e. Set point of 500A and a time delay of 1 Sec, at 500A the delay is 1 sec. and at 1000A the delay would be .25 sec.)
Please refer to the product Data Sheets for the time delay curves.