Phase Rotation; Ct And Vt Reversal - GE P642 Technical Manual

Chapter 5 - Configuration
5

PHASE ROTATION

The product provides a facility to maintain correct operation of all the protection functions even when the system
is running in a reverse phase sequence. This is achieved by the Phase Sequence setting in the SYSTEM CONFIG
column, and is available for all four setting groups.
You can configure the Phase Sequence setting to Standard ABC or Reverse ABC. This setting does not
perform any internal phase swapping of the analog channels.
The Phase Sequence setting affecs the sequence component calculation as follows (In this example, the positive
and negative sequence currents are shown. The same principle applies to voltages):
Standard ABC
Ī = 1/3(Ī + aĪ +a
1 A B
Ī = 1/3(Ī + aĪ +a
2 A B
Reverse ABC
2
Ī = 1/3(Ī + a Ī
1 A B
2
Ī = 1/3(Ī + a Ī
2 A B
where a is the operator 1Ð120°
The phase Sequence setting also affects the directional overcurrent protection as follows:
Standard ABC
Phase A: Use I and V
●
A
Phase B: Use I and V
●
B
Phase C: Use I and V
●
C
Reverse ABC
Phase A: Use I and -V
●
A
● Phase B: Use I and -V
B
Phase C: Use I and -V
●
C
5.1

CT AND VT REVERSAL

The product also provides VT and CT reversal settings (in the SYSTEM CONFIG column), which can be used in
applications where some or all of the voltage or current inputs are temporarily reversed, for example in pump
storage applications. These settings affect the order of the analog channels in the device and are set to emulate
the order of the channels on the power system. So assuming the settings emulate the change in phase
configuration on the power system, all the protection functions will naturally operate as per a standard phase
rotation system. The phase sequence calculations and the protection functions all remain unchanged.
96
2
Ī )
C
2
Ī )
C
+aĪ )
C
+aĪ )
C
BC
CA
AB
BC
CA
AB
P64x
P64x-TM-EN-1.3