GE Industrial Solutions Entellisys System User Manual - Manual (Page 73)

Single Point Relay protection 73
5
• Dropout Phase Loss – Phase loss relay has dropped out of pickup.
• Voltage Below Phase Loss Blocking Voltage – The voltages on all three phases have dropped
below the phase loss blocking voltage threshold.
• Voltage Above Phase Loss Blocking Voltage – The voltage on at least one of the three phases
has exceeded the phase loss blocking voltage threshold.
To view these events, click Sequence of Events on the Main Menu.
5.2.6 Reverse Power Relay
The Entellisys system provides a Reverse Power Relay that prevents an open primary on a
transformer from back-feeding the magnetizing current. The system performs this function by
comparing the magnitude and direction of the power in each phase to the set point. If, on any
phase, the direction of the power is reversed and the magnitude of the power is greater than the
set point for the specified time delay, the system opens or trips the circuit breaker or activates
an alarm.
The relay can be in three states:
• Pickup – If the reverse power 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
trips the appropriate circuit breaker or activates an alarm, and the relay is said to be in
Operate state.
• Drop out – The relay drops out of pickup when the reverse power drops below 97% of the
programmed threshold. The relay is said to be in Drop out state.
The power reversal pickup setting can be adjusted from 10 to 990 kW, in steps of 10 kW. The
power reversal delay setting can be adjusted from 0.5 second to 600 seconds in increments of
0.5 seconds.
5.2.6.1 Accuracy
Pickup accuracy is ± 4%. Trip time accuracy is ± 0.5 seconds.
5.2.6.2 Setup
To set the Trip and Alarm settings for the Reverse Power Relay
1. On the Main Menu, click User Settings, and then select Relay Protection.
2. On the Relay Protection screen, choose the circuit breaker number from the drop-down
menu and click Reverse Power.
The remainder of this section discusses the relay parameters that can be set in the Reverse
Power section of the Relay Protection screen as shown in Figure 5-9.
5.2.6.3 Trip settings
Relay Enabled: Select Enabled to enable the relay.
Pickup: Adjust the reverse power pickup from 10 to 990kW in increments of 10kW from the
Pickup Setting drop-down menu.