GE M60 Instruction Manual page 242

SYSTEM SETUP
These settings are critical for all features that have settings dependent on current measurements. When the relay is
ordered, the CT module must be specified to include a standard or sensitive ground input. As the phase CTs are connected
in wye (star), the calculated phasor sum of the three phase currents (IA + IB + IC = neutral current = 3Io) is used as the input
for the neutral overcurrent elements. In addition, a zero-sequence (core balance) CT which senses current in all of the
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
5
SETTINGS  SYSTEM SETUP  AC INPUTS  VOLTAGE BANK F5(M5)
 VOLTAGE BANK F5

Because energy parameters are accumulated, these values should be recorded and then reset immediately prior to
changing VT characteristics.
Two banks 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} 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
5-114
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
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
M60 MOTOR PROTECTION SYSTEM – INSTRUCTION MANUAL
CHAPTER 5: SETTINGS
Eq. 5-6
PHASE VT F5