3-24 D30 LINE DISTANCE PROTECTION SYSTEM – INSTRUCTION MANUALWIRING CHAPTER 3: INSTALLATION3Lightning strikes and ground surge currents can cause large momentary voltage differences between remote ends of thecommunication link. For this reason, surge protection devices are provided internally at both communication ports. Anisolated power supply with an optocoupled data interface also acts to reduce noise coupling. To ensure maximumreliability, ensure that all equipment has similar transient protection devices installed.Terminate both ends of the RS485 circuit with an impedance as shown in the figure.Figure 3-23: RS485 serial connection3.3.9.3 100Base-FX fiber optic portsThe fiber optic communication ports allow for fast and efficient communications between relays at 100 Mbps. Optical fibercan be connected to the relay supporting a wavelength of 1310 nm in multimode.Ensure that the dust covers are installed when the fiber is not in use. Dirty or scratched connectors can lead to high losseson a fiber link.3.3.10 IRIG-BIRIG-B is a standard time code format that allows stamping of events to be synchronized among connected devices. TheIRIG-B code allows time accuracies of up to 100 ns. Using the IRIG-B input, the D30 operates an internal oscillator with 1 μsresolution and accuracy. The IRIG time code formats are serial, width-modulated codes that can be either DC level shiftedor amplitude modulated (AM). Third party equipment is available for generating the IRIG-B signal; this equipment can use aglobal positioning system (GPS) satellite system to obtain the time reference so that devices at different geographiclocations can be synchronized.SCADA / PLC / computerOptocoupler DataUR-series deviceShield827757AA.CDRLast deviceZ (*)TZ (*) Terminating impedance atTeach end (typically 120 Ω and 1 nF)Twisted pair RS485 +RS485 –COMP 485COMRelayRelayGround shield at SCADA / PLC /computer only or atUR-series device onlyData OptocouplerUp to 32 devices,maximum 4000 feet(1200 m)Z (*)TRS485 +RS485 –COMP 485COMRS485 +RS485 –COMP 485COMCOM
