Ct/Vt Modules - GE UR Series B30 Instruction Manual

3.2 WIRING
3
Switchgear
ground bus
A CT/VT module can have voltage or current 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).
To connect the module, size 12 American Wire Gauge (AWG) is commonly used; the maximum size is 10 AWG.
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withdrawn from the chassis.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 can be used.
CT/VT modules with a sensitive ground input are also available. The ground CT input of the sensitive ground modules is 10
times more sensitive than the ground CT input of standard CT/VT modules. However, the phase CT inputs and phase VT
inputs are the same as those of regular CT/VT modules.
The above modules have enhanced diagnostics, when ordered as such, that can automatically detect CT/VT hardware fail-
ure 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 as follows. Twisted-pair
cabling on the zero-sequence CT is recommended.
3-12
AC or DC
Heavy copper conductor
or braided wire
B8b B8a B6a B6b B5b
FILTER SURGE
Figure 3–13: CONTROL POWER CONNECTION
Verify that the connection made to the relay terminals for nominal current of 1 A or 5 A matches the
secondary rating of the connected CTs. Unmatched CTs can result in equipment damage or inade-
quate protection.
B30 Bus 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