Ct/Vt Modules - GE L90 Instruction Manual

3.2 WIRING
An LED on the front of the control power module shows the status of the power supply:
LED INDICATION
CONTINUOUS ON
ON / OFF CYCLING
OFF
3
Switchgear
ground bus
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. Likewise, channels 2 and 6 are intended
for connection to phase B, and channels 3 and 7 are intended for connection to phase C.
Channels 4 and 8 are intended for connection to a single-phase source. For voltage inputs, these channel are labelled as
auxiliary voltage (VX). For current inputs, these channels are intended for connection to a CT between system neutral and
ground, and are labelled as ground current (IG).
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.
CAUTION
CT/VT modules may be ordered with a standard ground current input that is the same as the phase current input. 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withdrawn from the chassis.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. Current transformers with 1 to
50000 A primaries and 1 A or 5 A secondaries may be used.
The above modules are available with enhanced diagnostics. These modules can automatically detect CT/VT hardware
failure and take the relay out of service.
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.
3-12
POWER SUPPLY
OK
Failure
Failure
AC or DC
Heavy copper conductor
or braided wire
B8b B8a B6a B6b B5b
FILTER SURGE
Figure 3–13: CONTROL POWER CONNECTION
L90 Line Current Differential System
NOTE:
14 gauge stranded
wire with suitable
disconnect devices
is recommended.
+
+
–
LOW
HIGH
CONTROL
POWER
UR-series
protection system
3 HARDWARE
AC or DC
+
—
OPTIONAL
ETHERNET SWITCH
827759AA.CDR

3.2.4 CT/VT MODULES

GE Multilin