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10 APPLICATION OF SETTINGS
•
The type 8L CT/VT module U1 to U3 three-phase CT channels are connected to the neutral side window CTs with a
50 / 5 A ratio.
The following settings are applied in the EnerVista UR Setup software.
The VT channels are connected as follows.
•
The type 8L CT/VT module F5 to F7 three-phase VT channels are connected to the bus side three-phase VTs with a
138 / 0.115 kV ratio.
•
The type 8V CT/VT module M1 to M3 and M5 to M7 three-phase VT channels are connected to two tap VTs with a
1.25 / 0.25 kV ratio. The nominal voltage is calculated below for normal bank conditions and a nominal system voltage
of 138 kV (see impedance calculations the following sub-section).
The nominal bus phase VT voltage is:
The nominal tap VT voltage is:
Therefore, the tap VT secondary voltage is set as:
Where the VT ratio N
is calculated as:
tap(VT)
The following settings are applied in the EnerVista UR Setup software.
The following sources must be assigned for the protection functions indicated.
•
Source 1 (bus) is assigned with CT and VT banks connected to the bus, providing a signal source for overcurrent,
phase current unbalance, overvoltage, and undervoltage functions.
GE Multilin
13800
V
=
--------------- -
(
)
tap bus
3
b
×
138000 Z
C
V
=
-------------------------------- -
(
)
tap nominal
t
×
3
Z
C
V
(
tap nominal
V
=
-------------------------------- -
(
)
tap secondary
N
(
)
tap VT
125 kV
N
=
------------------- -
(
)
tap VT
0.25 kV
C70 Capacitor Bank Protection and Control System
=
79674.34 V
×
13800
4.08
171.41 V
=
---------------------------------- -
=
×
3
1894.42
171.41 V
)
34.28 V
=
----------------------- -
=
5
5
=
10.4 SETTING EXAMPLE
(EQ 10.1)
(EQ 10.2)
(EQ 10.3)
(EQ 10.4)
10.4.3 SOURCE ASSIGNMENT
10-13
10
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