3-28 C60 Breaker Protection System GE Multilin3.2 WIRING 3 HARDWARE33.2.9 CPU COMMUNICATION PORTSa) OVERVIEWIn addition to the faceplate RS232 port, the C60 provides a rear RS485 communication port.The CPU modules do not require a surge ground connection.Figure 3–26: CPU MODULE COMMUNICATIONS WIRINGb) RS485 PORTSRS485 data transmission and reception are accomplished over a single twisted pair with transmit and receive data alternat-ing over the same two wires. Through the use of the port, continuous monitoring and control from a remote computer,SCADA system, or PLC is possible.To minimize errors from noise, the use of shielded twisted pair wire is recommended. Correct polarity must also beobserved. For instance, the relays must be connected with all RS485 “+” terminals connected together, and all RS485 “–”terminals connected together. Though data is transmitted over a two-wire twisted pair, all RS485 devices require a sharedreference, or common voltage. This common voltage is implied to be a power supply common. Some systems allow theshield (drain wire) to be used as common wire and to connect directly to the C60 COM terminal (#3); others function cor-rectly only if the common wire is connected to the C60 COM terminal, but insulated from the shield.NOTE842722A3.CDR100Base-TCOMMON++——D1aD2aD3aD4bD4aBNCIRIG-BinputCPU VCo-axial cableShieldedtwisted-pairsGround atremotedeviceRS485COM2100Base-T100Base-TCOMMON++——D1aD2aD3aD4bD4aBNCIRIG-BinputCPU UCo-axial cableShieldedtwisted-pairsGround atremotedeviceRS485COM2100Base-T100Base-FXPort 1Port 2100Base-FXTx1 Rx1COMMON++——D1aD2aD3aD4bD4aBNCIRIG-BinputCPU TCo-axial cableShieldedtwisted-pairsMM fiber-optic cableGround atremotedeviceRS485COM2100Base-FX100Base-FXTx2 Rx2Tx3 Rx3Tx1 Rx1Port 3Port 1Port 2Port 3Port 1Port 2Port 3100Base-FXTx1 Rx1
