CHAPTER 3: INSTALLATION WIRINGB30 BUS DIFFERENTIAL SYSTEM – INSTRUCTION MANUAL 3-253Lightning 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 B30 operates an internal oscillator with 1 μsresolution and accuracy. The IRIG time code formats are serial, pulse width-modulated codes that can be either DC levelshifted or amplitude modulated (AM). The GE MultiSync 100 1588 GPS Clock as well as third-party equipment are availablefor generating the IRIG-B signal; this equipment can use a global positioning system (GPS) satellite system to obtain thetime reference so that devices at different geographic locations can be synchronized.
