A CT/VT module may 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withdrawn from the chassis.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.
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 phase voltage channels are used for most metering and protection purposes. The auxiliary voltage channel is used as
input for the synchrocheck and volts-per-hertz features.
The L60 uses a special CT/VT module not available on other UR-series relays. This type 8P module has four current inputs
and special communications inputs/outputs for interfacing with PLCs. The communications interface requires an external
DC source (station battery) to drive inputs/outputs as shown in the L60 channel communications section in this chapter.
Substitute the tilde "~" symbol with the slot position of the module in the following figure.
Figure 3–11: 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-
L60 Line Phase Comparison System
3.2.4 CT AND VT MODULES