CHAPTER 5: SETPOINTS
489 GENERATOR MANAGEMENT RELAY – INSTRUCTION MANUAL 5–49
and the phase rotation is not the same as the setpoint. Loss of VT fuses cannot be
detected when the generator is offline and could lead to maloperation of this element. If
the VT type is selected as “None”, the phase reversal protection is disabled.
5.7.5 Underfrequency
PATH: SETPOINTS ZV S6 VOLTAGE ELEM. ZV UNDERFREQUENCY
It may be undesirable to enable the underfrequency elements until the generator is online.
This feature can be blocked until the generator is online and the block time expires. From
that point forward, the underfrequency trip and alarm elements will be active. A value of
zero for the block time indicates that the underfrequency protection is active as soon as
voltage exceeds the cutoff level (programmed as a multiple of the generator rated phase-
phase voltage). Frequency is then measured. Once the frequency of Vab is less than the
underfrequency setpoints, for the period of time specified, a trip or alarm will occur. There
are dual level and time setpoints for the trip element.
1 UNDERFREQUENCY [Z] BLOCK UNDERFREQUENCY
FROM ONLINE: 1 s
Range: 0 to 5 s in steps of 1
MESSAGE
VOLTAGE LEVEL
CUTOFF: 0.50 x Rated
Range: 0.50 to 0.99 × Rated in steps of
0.01
MESSAGE
UNDERFREQUENCY
ALARM: Off
Range: Off, Latched, Unlatched
MESSAGE
ASSIGN ALARM
RELAYS (2-5): ---5
Range: Any combination of Relays 2 to
5
MESSAGE
UNDERFREQUENCY
ALARM LEVEL: 59.50 Hz
Range: 20.00 to 60.00 Hz in steps of
0.01
MESSAGE
UNDERFREQUENCY
ALARM DELAY: 5.0 s
Range: 0.1 to 5000.0 s in steps of 0.1
MESSAGE
UNDERFREQUENCY
ALARM EVENTS: Off
Range: On, Off
MESSAGE
UNDERFREQUENCY
TRIP: Off
Range: Off, Latched, Unlatched
MESSAGE
ASSIGN TRIP
RELAYS (1-4): 1---
Range: Any combination of Relays 1 to
4
MESSAGE
UNDERFREQUENCY
TRIP LEVEL1: 59.50 Hz
Range: 20.00 to 60.00 Hz in steps of
0.01
MESSAGE
UNDERFREQUENCY
TRIP DELAY1: 60.0 s
Range: 0.1 to 5000.0 s in steps of 0.1
MESSAGE
UNDERFREQUENCY
TRIP LEVEL2: 58.00 Hz
Range: 20.00 to 60.00 Hz in steps of
0.01
MESSAGE
UNDERFREQUENCY
TRIP DELAY2: 30.0 s
Range: 0.1 to 5000.0 s in steps of 0.1
Courtesy of NationalSwitchgear.com
To Next Page
Need help?
General