GE Industrial Solutions Entellisys System User Manual - Manual (Page 64)

Single point functions 64
5
5.2.2.5 Usage
Event logging
The following events are logged for the Overvoltage relay in the Entellisys HMI:
• Alarm Pickup Overvoltage – Alarm only overvoltage relay has entered pickup
• Alarm Overvoltage – Alarm only overvoltage relay has operated
• Alarm Dropout Overvoltage – Alarm only overvoltage relay has dropped out of pickup
• Pickup Overvoltage – Overvoltage relay has entered pickup
• Breaker Trip Overvoltage – Overvoltage relay has operated
• Dropout Overvoltage – Overvoltage relay has dropped out of pickup
To view these events, click Sequence of Events on the Main Menu.
5.2.3 Over Frequency Relay
The Entellisys System executes the Over Frequency Relay function by comparing the
fundamental frequency of the phase A voltage to the programmed pickup set point.
The relay can be in three states:
• Pickup – If the frequency of the phase A voltage is greater 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 frequency drops below 97% of the
programmed threshold. The relay is said to be in Drop out state.
The system trips the appropriate circuit breaker or activates an alarm if the frequency is greater
than the pickup set point for the specified time delay.
5.2.3.1 Accuracy
Pickup accuracy is less than ± 0.1 Hz. Trip time accuracy is ± 0.1 seconds.
Blocking voltage option: A 'blocking voltage' user-defined input option is provided. The over
frequency relay function is not performed if the blocking voltage option is enabled and the
voltage is less than the blocking voltage. If the Over Frequency Relay goes into pickup, and the
voltages subsequently drop below the blocking voltage, the relay goes out of pickup and the
delay is reset.