The power supply module provides 48 V DC power for dry contact input connections and a critical failure relay (see TYPI-
CAL WIRING DIAGRAM). The critical failure relay is a Form-C that will be energized once control power is applied and the
relay has successfully booted up with no critical self-test failures. If any of the on-going self-test features detect a critical
failure or control power is lost, the relay will de-energize.
A CT/VT module may have voltage inputs on channels 1 through 4 inclusive, or channels 5 through 8 inclusive. Channels 1
and 5 are intended for connection to phase A, and are labeled as such in the relay. Channels 2 and 6 are intended for con-
nection to phase B, and are labeled as such in the relay. Channels 3 and 7 are intended for connection to phase C and are
labeled as such in the relay. Channels 4 and 8 are intended for connection to a single phase source. If voltage, this channel
is labelled the auxiliary voltage (VX). If current, this channel is intended for connection to a CT between a system neutral
and ground, and is labelled the ground current (IG).
a) AC CURRENT TRANSFORMER INPUTS
VERIFY THAT THE CONNECTION MADE TO THE RELAY NOMINAL CURRENT OF 1 A OR 5 A MATCHES
THE SECONDARY RATING OF THE CONNECTED CTs. UNMATCHED CTs MAY RESULT IN EQUIPMENT
DAMAGE OR INADEQUATE PROTECTION.
The CT/VT module may be ordered with a standard ground current input that is the same as the phase current inputs (type
8A) or with a sensitive ground input (type 8B) which is 10 times more sensitive (see the Technical Specifications section for
more details). Each AC current input has an isolating transformer and an automatic shorting mechanism that shorts the
input when the module is withdrawn from the chassis. There are no internal ground connections on the current inputs. Cur-
rent 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 CT so that ground fault current will be detected is shown below. Twisted pair
cabling on the zero sequence CT is recommended.
Figure 3–9: CONTROL POWER CONNECTION
L90 Line Differential Relay
3.2.4 CT/VT MODULES
GE Power Management