Reactive Power - GE 489 Instruction Manual

4.8 S7 POWER ELEMENTS
PATH: SETPOINTS S7 POWER ELEMENTS

REACTIVE POWER

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4
In a motor/generator application, it may be desirable not to trip or alarm on reactive power until the machine is online and
the field has been applied. Therefore, this feature can be blocked until the machine is online and adequate time has expired
during which the field had been applied. From that point forward, the reactive power trip and alarm elements will be active.
A value of zero for the block time indicates that the reactive power protection is active as soon as both current and voltage
are measured regardless of whether the generator is online or offline. Once the 3-phase total reactive power exceeds the
positive or negative level, for the specified delay, a trip or alarm will occur indicating a positive or negative Mvar condition.
The level is programmed in per unit of generator rated Mvar calculated from the rated MVA and rated power factor. The
reactive power elements can be used to detect loss of excitation. If the VT type is selected as "None" or VT fuse loss is
detected, the reactive power protection is disabled. Rated Mvars for the system can be calculated as follows:
For example, given Rated MVA = 100 MVA and Rated Power Factor = 0.85, we have
Rated Mvars
4-46
REACTIVE POWER
ð
BLOCK Mvar ELEMENT
ENTER
ð
ESCAPE FROM START: 1 s
REACTIVE POWER
ESCAPE
ALARM: Off
MESSAGE
ASSIGN ALARM
ESCAPE
RELAYS (2-5): ---5
MESSAGE
POSITIVE Mvar ALARM
ESCAPE
LEVEL: 0.85 x Rated
MESSAGE
NEGATIVE Mvar ALARM
ESCAPE
LEVEL: 0.85 x Rated
MESSAGE
POSITIVE Mvar ALARM
ESCAPE
DELAY: 10.0 s
MESSAGE
NEGATIVE Mvar ALARM
ESCAPE
DELAY: 1.0 s
MESSAGE
REACTIVE POWER ALARM
ESCAPE
EVENTS: Off
MESSAGE
REACTIVE POWER
ESCAPE
TRIP: Off
MESSAGE
ASSIGN TRIP
ESCAPE
RELAYS (1-4): 1---
MESSAGE
POSITIVE Mvar TRIP
ESCAPE
LEVEL: 0.80 x Rated
MESSAGE
NEGATIVE Mvar TRIP
ESCAPE
LEVEL: 0.80 x Rated
MESSAGE
POSITIVE Mvar TRIP
ESCAPE
DELAY: 20.0 s
MESSAGE
NEGATIVE Mvar TRIP
ESCAPE
DELAY: 20.0 s
MESSAGE
1
–
× ( (
Rated MVA sin cos Rated PF
=
489 Generator Management Relay
Range: 0 to 5000 s in steps of 1
Range: Off, Latched, Unlatched
Range: Any combination of Relays 2 to 5
Range: 0.02 to 2.01 × Rated in steps of 0.01
Range: 0.02 to 2.01 × Rated in steps of 0.01
Range: 0.2 to 120.0 s in steps of 0.1
Note: Lagging vars, overexcited
Range: 0.2 to 120.0 s in steps of 0.1
Note: Leading vars, underexcited
Range: On, Off
Range: Off, Latched, Unlatched
Range: Any combination of Relays 1 to 4
Range: 0.02 to 2.01 × Rated in steps of 0.01
Range: 0.02 to 2.01 × Rated in steps of 0.01
Range: 0.2 to 120.0 s in steps of 0.1
Note: Lagging vars, overexcited
Range: 0.2 to 120.0 s in steps of 0.1
Note: Leading vars, underexcited
1
–
) ) × ( ( ) )
100 sin cos 0.85
=
4 SETPOINTS
4.8.2 REACTIVE POWER
52.67 Mvars
(EQ 4.25)
=
GE Multilin