GE C70 Instruction Manual page 237

CHAPTER 5: SETTINGS
circuit primary conductors, or a CT in a neutral grounding conductor can also be used. For this configuration, the ground
CT primary rating must be entered. To detect low level ground fault currents, the sensitive ground input can be used. In this
case, the sensitive ground CT primary rating must be entered. See chapter 3 for more details on CT connections.
Enter the rated CT primary current values. For both 1000:5 and 1000:1 CTs, the entry would be 1000. For correct operation,
the CT secondary rating must match the setting (which must also correspond to the specific CT connections used).
The following example illustrates how multiple CT inputs (current banks) are summed as one source current. Given the
following current banks:
• F1: CT bank with 500:1 ratio
• F5: CT bank with 1000:1 ratio
• M1: CT bank with 800:1 ratio
The following rule applies:
1 pu is the highest primary current. In this case, 1000 is entered and the secondary current from the 500:1 ratio CT is
adjusted to that created by a 1000:1 CT before summation. If a protection element is set up to act on SRC 1 currents, then
a pickup level of 1 pu operates on 1000 A primary.
The same rule applies for current sums from CTs with different secondary taps (5 A and 1 A).
5.5.1.2 Voltage banks
SETTINGS  SYSTEM SETUP  AC INPUTS  VOLTAGE BANK F5(U5)
 VOLTAGE BANK F5

Three bank of phase/auxiliary VTs can be set, where voltage banks are denoted in the following format (X represents the
module slot position letter):
Xa, where X = {F, M, U} and a = {5}
See the Introduction to AC Sources section at the beginning of this chapter for additional details.
With VTs installed, the relay can perform voltage measurements as well as power calculations. Enter the
made to the system as "Wye" or "Delta." An open-delta source VT connection is entered as "Delta."
CONNECTION
The nominal
PHASE VT F5 SECONDARY
nominal voltage is applied to the VT primary.
NOTE
For example, on a system with a 13.8 kV nominal primary voltage and with a 14400:120 volt VT in a delta
connection, the secondary voltage is 115; that is, (13800 / 14400) × 120. For a wye connection, the voltage
value entered must be the phase to neutral voltage, which is 115 /
On a 14.4 kV system with a delta connection and a VT primary to secondary turns ratio of 14400:120, the
voltage value entered is 120; that is, 14400 / 120.
C70 CAPACITOR BANK PROTECTION AND CONTROL SYSTEM – INSTRUCTION MANUAL
SRC 1 = F1 F5 M1 + +
PHASE VT F5

CONNECTION: Wye
PHASE VT F5

SECONDARY: 66.4 V
PHASE VT F5

RATIO: 1.00 :1
AUXILIARY VT F5

CONNECTION: Vag
AUXILIARY VT F5

SECONDARY: 66.4 V
AUXILIARY VT F5

RATIO: 1.00 :1
voltage setting is the voltage across the relay input terminals when
Range: Wye, Delta
Range: 25.0 to 240.0 V in steps of 0.1
Range: 1.00 to 24000.00 in steps of 0.01
Range: Vn, Vag, Vbg, Vcg, Vab, Vbc, Vca
Range: 25.0 to 240.0 V in steps of 0.1
Range: 1.00 to 24000.00 in steps of 0.01
= 66.4.
3
SYSTEM SETUP
Eq. 5-6
5
PHASE VT F5
5-113