3-14 B90 LOW IMPEDANCE BUS DIFFERENTIAL SYSTEM – INSTRUCTION MANUALWIRING CHAPTER 3: INSTALLATION3An 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 panelFigure 3-13: Control power connection3.3.4 CT and VT modulesInformation 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current input has an isolating transformer and an automatic shorting mechanism that shorts the input when themodule is withdrawn from the chassis. There are no internal ground connections on the current inputs. Currenttransformers 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 neutralvoltage from the open-delta VT.All CT and VT modules are available with enhanced diagnostics. These modules can automatically detect CT/VT hardwarefailure and take the relay out of service.LED indication Power supplyContinuous on OKOn/off cycling FailureOff Failure or no powerVerify that the connection made to the relay nominal current of 1 A or 5 A matches the secondaryrating of the connected CTs. Unmatched CTs may result in equipment damage or inadequateprotection.Substitute the tilde “~” symbol with the slot position of the module in the following figure.
