GE D90 Plus Instruction Manual page 66

ELECTRICAL INSTALLATION
56
The CT secondaries should be connected to the AC terminals of the D90
shorting-type test switch or shorting-type terminal blocks in order to facilitate safe
withdrawal of the AC module.
There are no internal ground connections on the current inputs. Current transformers with
1 to 50000 A primaries and 1 A or 5 A secondaries may be used.
CT connections for both ABC and ACB phase rotations are identical as shown in the typical
wiring diagram.
The exact placement of a zero-sequence core balance CT to detect ground fault current is
shown below. Twisted-pair cabling on the zero-sequence CT is recommended.
Figure 25: Zero-sequence core-balance CT installation
The phase voltage channels are used for most metering and protection purposes. The
auxiliary voltage channel is used as an input for features such as synchrocheck, volts per
hertz, and auxiliary undervoltage.
A typical AC module wiring diagram is shown below. Substitute the tilde "~" symbol with
the slot position of the AC module.
PLUS
D90 LINE DISTANCE PROTECTION SYSTEM – INSTRUCTION MANUAL
CHAPTER 3: INSTALLATION
Plus
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