High-Set Phase Overcurrent - GE 489 Instruction Manual

4.6 S5 CURRENT ELEMENTS
The 489 detects ground directional by using two measurement quantities: V
determines if a ground fault is within the generator or not. This function should be coordinated with the 59GN element (95%
stator ground protection) to ensure proper operation of the element. Particularly, this element should be faster. This ele-
ment must use a core balance CT to derive the I
blocked for neutral voltages, V
The pickup level for the ground current elements is programmable as a multiple of the CT. The 50:0.025 CT is
intended for very sensitive detection of ground faults and its nominal CT rating for the 489 is 50:0.025.
NOTE
For example, if the ground CT is 50:0.025, a pickup of 0.20 would be 0.20 x 5 = 1 A primary. If the ground CT is 50:0.025, a
pickup of 0.05 would be 0.05 x 5 = 0.25 A primary. Refer to Appendix A.1: Stator Ground Fault on page A–1 for additional
details
4
GROUNDING SWITCH
59G
TO Vneutral OF EACH 489
PATH: SETPOINTS S5 CURRENT ELEMENTS
HIGH-SET PHASE O/C
[ENTER] for more
If any individual phase current exceeds the pickup level for the specified trip time a trip will occur if the feature is enabled.
The element operates in both online and offline conditions. This element can be used as a backup feature to other protec-
tion elements. In situations where generators are connected in parallel this element would be set above the maximum cur-
rent contribution from the generator on which the protection is installed. With this setting, the element would provide proper
selective tripping. The basic operating time of the element with no time delay is 50 ms at 50/60 Hz.
4-32
signal. Polarity is critical in this element. The protection element is
0
, below 2.0 V secondary.
0
AUXILIARY
CONTACT
Figure 4–5: GROUND DIRECTIONAL DETECTION
HIGH-SET PHASE O/C
ð
HIGH-SET PHASE O/C
ENTER
ð
TRIP: Off
ESCAPE
ASSIGN TRIP
ESCAPE
RELAYS (1-4): 1---
MESSAGE
HIGH-SET PHASE O/C
ESCAPE
PICKUP: 5.00 x CT
MESSAGE
HIGH-SET PHASE O/C
ESCAPE
DELAY: 1.00 s
MESSAGE
489 Generator Management Relay
and I . The angle between these quantities
0 0
C(B)
C(B)
A
A
B(C)
B(C)

4.6.10 HIGH-SET PHASE OVERCURRENT

Range: Off, Latched, Unlatched
Range: Any combination of Relays 1 to 4
Range: 0.15 to 20.00 x CT in steps of 0.01
Range: 0.00 to 100.00 s in steps of 0.01
4 SETPOINTS
I0
TO 50:0.025
50:0.025 GROUND
INPUTS
808812A3.CDR
GE Multilin