GE Industrial Solutions Entellisys 4.0 System User Manual - Manual (Page 86)

Single point functions 86
5
5.2.8 High Resistance Ground Fault Detection Relay
The Entellisys system provides an optional High Resistance Ground Fault Detection (HRGF)
Function that is an alarm-only function that does not trip the circuit breaker. The relay requires
an additional 10A ground CT and will detect a fault by measuring the current through the
resistance ground circuit of the substation transformer.
The system will indicate that a ground fault event occurred and on which phase. See High
Resistance Ground Fault Location Relay on page 88 to locate the specific feeder.
The relay can be in three states:
•
Pickup – If the ground current in any phase is more than the pickup set point, the relay goes
into pickup, and is said to enter Pickup state.
•
Operate – If the relay stays in pickup state for a specified pick up delay time, the system
activates an alarm, and the relay is said to be in Operate state.
•
Drop out – The relay drops out of pickup when the ground current drops below 97% of the
programmed threshold. The relay is said to be in Drop out state.
The HRGF pickup is programmable from 0.1 amps to 10.0 amps of ground current in increments
of 0.1 amps. The delay setting is programmable from 0.5 to 5 seconds in increments of
0.1 second. A constant time curve is used for HRGF. If the ground current is above the pickup
threshold, the system logs an event. If the ground current remains above the threshold for
longer than the delay setting, the system logs an event and activates an alarm.
NOTE: Multi-Source Ground Fault is not available in High Resistance Systems
5.2.8.1 Accuracy
Pickup accuracy is ± 10%. For 1 Amp and below, the accuracy is ± 10% of 1 Amp
5.2.8.2 Setup
The HRGF relay is a per line-up option.
To set the Alarm settings for the HRGF relay
1. On the Main Menu, click User Settings, and then select Advanced Protection.
2. On the High Resistance GF tab (User Settings, Advanced Protection screen), choose the
circuit breaker number from the drop-down menu and click High Resistance GF.
The remainder of this section discusses the relay parameters that can be set in the High
Resistance GF section of the Relay Protection screen as shown in Figure 5-11.
NOTE: High Resistance Detection and Location Relays are only available on breakers which
have a ground CT.
5.2.8.3 Alarm settings
Relay Enabled: Select Enabled to enable the relay.