Bank Voltage Differential Settings - GE C70 Instruction Manual

9.4 SETTING EXAMPLE
Table 9–1: UNBALANCE VALUES FOR MAXIMUM SYSTEM CONDITIONS
n s
Z
f
C
1894.42 Ω
0
1894.42 Ω
1
1894.42 Ω
2
3 1894.42 Ω
4 1894.42 Ω
5 1894.42 Ω
1894.42 Ω
6
1894.42 Ω
7
1894.42 Ω
8
9 1894.42 Ω
10 1894.42 Ω
To check the limits of protection sensitivity, the same calculations are repeated for the minimum system conditions, which
are considered to be 0.85 pu of nominal system voltage.
The minimum line to neutral system voltage is:
The following table summarizes the unbalance values during minimum system conditions.
Table 9–2: UNBALANCE VALUES FOR MINIMUM SYSTEM CONDITIONS
n
s
Z
f
C
0 1894.42 Ω
1 1894.42 Ω
1894.42 Ω
2
1894.42 Ω
3
1894.42 Ω
4
5 1894.42 Ω
6 1894.42 Ω
7 1894.42 Ω
1894.42 Ω
8
1894.42 Ω
9
1894.42 Ω
10
The balance values during minimum operating conditions may be used to check sensitivity.
The bank configuration, CT location, and VT locations allow applying three voltage differential elements:
9
• An 87V-1 differential element measuring the differential voltage between the two bottom taps.
• An 87V-2 differential element measuring the differential voltage between the upper capacitor string and bottom capaci-
tor can for string 1.
• An 87V-3 differential element measuring the differential voltage between the upper capacitor string and bottom capaci-
tor can for string 2.
9-16
sf V V
Z
tap1 tap2
C
1894.42 Ω
175.37 V 175.37 V
1849.41 Ω
175.37 V 179.64 V
1804.40 Ω
175.37 V 184.12 V
1759.39 Ω 175.37 V 188.83 V
1714.38 Ω 175.37 V 193.79 V
1669.38 Ω 175.37 V 199.01 V
1624.37 Ω
175.37 V 204.52 V
1579.36 Ω
175.37 V 210.35 V
1534.35 Ω
175.37 V 216.52 V
1489.34 Ω 175.37 V 223.07 V
1444.34 Ω 175.37 V 230.02 V
×
0.85 V
nom
V ------------------------------ -
= =
min
3
V V
sf
Z
tap1 tap2
C
1894.42 Ω 145.70 V 145.70 V
1849.41 Ω 145.70 V 149.24 V
1804.40 Ω
145.70 V 152.97 V
1759.39 Ω
145.70 V 156.88 V
1714.38 Ω
145.70 V 161.00 V
1669.38 Ω 145.70 V 165.34 V
1624.37 Ω 145.70 V 169.92 V
1579.36 Ω 145.70 V 174.76 V
1534.35 Ω
145.70 V 179.89 V
1489.34 Ω
145.70 V 185.32 V
1444.34 Ω
145.70 V 191.10 V
C70 Capacitor Bank Protection and Control System
V OV
top
81340.00 V 1.000 pu
81335.73 V 1.024 pu
81331.25 V 1.050 pu
81326.54 V 1.077 pu
81321.58 V 1.105 pu
81316.36 V 1.135 pu
81310.85 V 1.167 pu
81305.02 V 1.200 pu
81298.85 V 1.235 pu
81292.30 V 1.273 pu
81285.35 V 1.313 pu
0.85 × 138000 V
------------------------------------------- - 67723 V
=
3
V OV
top
67577.30 V 1.000 pu
67573.76 V 1.024 pu
67570.03 V 1.050 pu
67566.12 V 1.077 pu
67562.00 V 1.105 pu
67557.66 V 1.135 pu
67553.08 V 1.167 pu
67548.24 V 1.200 pu
67543.11 V 1.235 pu
67537.68 V 1.273 pu
67531.90 V 1.313 pu

9.4.5 BANK VOLTAGE DIFFERENTIAL SETTINGS

9 APPLICATION OF SETTINGS
V V I
diff tap ( ) diff string ( ) unbal
0.0000 pu 0.0000 pu 0.0000 pu
0.0249 pu 0.0249 pu 0.0209 pu
0.0510 pu 0.0510 pu 0.0429 pu
0.0785 pu 0.0785 pu 0.0660 pu
0.1074 pu 0.1074 pu 0.0904 pu
0.1379 pu 0.1379 pu 0.1160 pu
0.1701 pu 0.1701 pu 0.1431 pu
0.2041 pu 0.2041 pu 0.1717 pu
0.2401 pu 0.2401 pu 0.2020 pu
0.2783 pu 0.2783 pu 0.2341 pu
0.3188 pu 0.3188 pu 0.2682 pu
(EQ 9.22)
V V I
( ) ( )
diff tap diff string unbal
0.0000 pu 0.0000 pu 0.0000 pu
0.0207 pu 0.0207 pu 0.0174 pu
0.0424 pu 0.0424 pu 0.0357 pu
0.0652 pu 0.0652 pu 0.0549 pu
0.0893 pu 0.0893 pu 0.0751 pu
0.1146 pu 0.1146 pu 0.0964 pu
0.1413 pu 0.1413 pu 0.1189 pu
0.1696 pu 0.1696 pu 0.1426 pu
0.1995 pu 0.1995 pu 0.1678 pu
0.2312 pu 0.2312 pu 0.1945 pu
0.2649 pu 0.2649 pu 0.2228 pu
GE Multilin