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DGP Digital Generator Protection System GE Power Management
2.3 PROTECTION FUNCTION SETTINGS 2 CALCULATION OF SETTINGS
2
2.3.8 STATOR GROUND FAULT 64G-1
Algorithm: 64G-1 operates if following condition is met:
V
N1
≥
PICKUP
for time > TL4 seconds
where:
V
N1
= Neutral voltage of fundamental frequency
PICKUP
= 64G-1 pickup setting
TL4
= timer TL4 setting
Setting 1103:
PICKUP
of 64G-1 should be set with a safe margin above the highest voltage (fundamental fre-
quency) expected at the generator neutral under normal operating conditions. Timer TL4 should be set with a
safe margin above the longest clearing time for power system faults that are outside of the generator protection
zone.
For the sample generator system,
set 1103:
PICKUP
= 5.0 volts
set 1104:
TL4
= 1 second or higher
2.3.9 STATOR GROUND FAULT 64G-2
Algorithm: 64G-2 operates when the following condition is met:
The only setting required for this optional function is for timer TL5 (Setting 1203:
TL5
) to provide a short delay
for security of the function.
For the sample generator system,
set 1203:
TL5
= 0.10 second.
2.3.10 STATOR GROUND FAULT 27TN
Algorithm: 27TN operates when the following conditions are met (see Figure 1–5: SIMPLE LOGIC DIAGRAM –
64G1, 64G2, 51GN, AND 24 on page 1–14 for the logic diagram):
V
N3
< 27TN PICKUP and
V
1
> 25V for time > TL20
where:
V
N3
= Third harmonic voltage at generator neutral.
V
1
= Positive sequence voltage at generator terminals.
TL20 = Timer TL20 (Setting 3004:
TL20
).
Setting 1302:
PICKUP
should be set as sensitive as the
V
N3
characteristic of the generator allows without loss
of security. A flexible window of power can be established to enhance security of 27TN. For example, assume
that the available
V
N3
is below 27TN pickup for power outputs in the range of 50 to 80 watts. The flexible win-
dow is provided by Settings 3005:
FORPWR-L
and 3006:
FORPWR-H
, which can be set at 47 and 85 watts
(based on margin of about 5%) respectively to inhibit the function between the limits. This function can also be
blocked when the generator is off-line; refer to Setting 2501:
SELBKDI1
.
V
N
3
V
P
3
3
⁄()
V
N
3
+
--------------------------------------- 0.15 for time >TL5 seconds
≤
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