GE 489 - Manual (Page 82)

4-32 489 Generator Management Relay GE Multilin
4.6 S5 CURRENT ELEMENTS 4 SETPOINTS
4
The 489 detects ground directional by using two measurement quantities: V
0
and I
0
. The angle between these quantities
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
0
signal. Polarity is critical in this element. The protection element is
blocked for neutral voltages, V
0
, below 2.0 V secondary.
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.
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
Figure 4–5: GROUND DIRECTIONAL DETECTION
4.6.10 HIGH-SET PHASE OVERCURRENT
PATH: SETPOINTS ÖØ S5 CURRENT ELEMENTS ÖØ HIGH-SET PHASE O/C
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.
„ HIGH-SET PHASE O/C
„ [ENTER] for more
HIGH-SET PHASE O/C
TRIP: Off
Range: Off, Latched, Unlatched
ASSIGN TRIP
RELAYS (1-4): 1---
Range: Any combination of Relays 1 to 4
HIGH-SET PHASE O/C
PICKUP: 5.00 x CT
Range: 0.15 to 20.00 x CT in steps of 0.01
HIGH-SET PHASE O/C
DELAY: 1.00 s
Range: 0.00 to 100.00 s in steps of 0.01
NOTE
59G
A A
C(B) C(B)
B(C) B(C)
TO 50:0.025
GROUND
INPUTS
50:0.025
I0
TO Vneutral OF EACH 489
AUXILIARY
CONTACT
GROUNDING SWITCH
808812A3.CDR
ENTER
ESCAPE
р
р
MESSAGE
ESCAPE
MESSAGE
ESCAPE
MESSAGE
ESCAPE