SETTINGS EXAMPLE
167KVAR,
825V
Based on the bank configuration, CT connections, and VTs connections, a C70 model is chosen with three CT/VT modules:
two type 8L modules (in slots F and U) and one type 8V module (in slot M) to provide following protection functionality.
•
Negative-sequence instantaneous overcurrent (ANSI 50_2) to provide fast backup protection against arcing within
capacitor bank
•
Phase overvoltage (ANSI 59B) to provide protection against overvoltages
•
Bank overcurrent protection, phase instantaneous overcurrent (ANSI 50P), neutral instantaneous overcurrent (ANSI
50N) and phase time overcurrent (ANSI 51P) to provide protection against major faults within the capacitor bank
•
Bank undervoltage (ANSI 27P) to detect loss of bus voltage and trip the bank
•
Voltage differential (ANSI 87V) to detect failure of one or more capacitor elements in a given string. Three voltage
differential elements can be set for this application: one between two tap voltages (ANSI 87V-1) and two between the
bus voltage and tap voltage in both strings (ANSI 87V-2 and 87V-3).
•
Phase current unbalance (ANSI 60P) to detect failure of one or more capacitor elements in a given string
8.4.2 VT and CT setup
The CT and VT connections are shown in the previous figure. The CT channels are connected as follows:
8
•
The type 8L CT/VT module F1 to F3 three-phase CT channels are connected to the bus side three-phase CTs with a
120 / 5 A ratio
•
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.
8-12
Figure 8-12: Sample capacitor bank configuration
138 kV
120/5A
50/5A
1250/250 V
C70 CAPACITOR BANK PROTECTION AND CONTROL SYSTEM – INSTRUCTION MANUAL
51P
50P
59B
138 kV/
0.115 kV/
3
500 kvar
11620 V
`
87V
CHAPTER 8: APPLICATION OF SETTINGS
C70 CAPACITOR BANK RELAY
51N
50_2
27P
60P
(C)
60P
(B)
60P
(A)
834764A1.CDR