GE G30 Instruction Manual page 586

OVERVIEW CHAPTER 8: APPLICATION OF SETTINGS
Figure 8-1: Typical wiring, VT on the high-voltage side of the transformer
The two sources are configured as follows.
The generator step-up (GSU) transformer is lagging by –30° (from the line side to the generator side). Take note of the CT
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polarities in wiring diagram. These are necessary to correctly meter forward power. Loss of excitation and reverse power
are to be assigned to source 2.
The transformer phase shift setting must compensate the measured relay currents for both the actual phase shift of the
transformer, and any phase due to the CT polarities and connections.
The difference seen by the differential is the transformer phase shift plus the CT phase shift, or –30° + (–180°) = –210°. The
transformer configuration is therefore as shown in the following figure.
8-2 G30 GENERATOR PROTECTION SYSTEM – INSTRUCTION MANUAL