3-14 B90 LOW IMPEDANCE BUS DIFFERENTIAL SYSTEM – INSTRUCTION MANUAL
WIRING CHAPTER 3: INSTALLATION
3
An LED on the front of the control power module shows the status of the power supply, as outlined in the table.
Table 3-2: Power supply LED on front panel
Figure 3-13: Control power connection
3.3.4 CT and VT modules
Information on the CT and VT modules for the B90 relay is shown here.
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module is withdrawn from the chassis.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.
Each B90 voltage input is intended for monitoring a single-phase voltage. The may include phase voltages or neutral
voltage from the open-delta VT.
All CT and VT modules are available with enhanced diagnostics. These modules can automatically detect CT/VT hardware
failure and take the relay out of service.
LED indication Power supply
Continuous on OK
On/off cycling Failure
Off Failure or no power
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.
Substitute the tilde “~” symbol with the slot position of the module in the following figure.
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