3-24 D30 Line Distance Protection System GE Multilin3.2 WIRING 3 HARDWARE3manner without exceeding driver capability. For larger systems, additional serial channels must be added. It is also possibleto use commercially available repeaters to have more than 32 relays on a single channel. Star or stub connections shouldbe avoided entirely.Lightning strikes and ground surge currents can cause large momentary voltage differences between remote ends of thecommunication link. For this reason, surge protection devices are internally provided at both communication ports. An iso-lated power supply with an optocoupled data interface also acts to reduce noise coupling. To ensure maximum reliability, allequipment should have similar transient protection devices installed.Both ends of the RS485 circuit should also be terminated with an impedance as shown below.Figure 3–25: RS485 SERIAL CONNECTIONc) 10BASE-FL AND 100BASE-FX FIBER OPTIC PORTSENSURE THE DUST COVERS ARE INSTALLED WHEN THE FIBER IS NOT IN USE. DIRTY OR SCRATCHEDCONNECTORS CAN LEAD TO HIGH LOSSES ON A FIBER LINK.OBSERVING ANY FIBER TRANSMITTER OUTPUT MAY CAUSE INJURY TO THE EYE.The fiber optic communication ports allow for fast and efficient communications between relays at 10 Mbps or 100 Mbps.Optical fiber may be connected to the relay supporting a wavelength of 820 nm in multi-mode or 1310 nm in multi-modeand single-mode. The 10 Mbps rate is available for CPU modules 9G and 9H; 100Mbps is available for modules 9H, 9J, 9K,9L, 9M, 9N, 9P, and 9R. The 9H, 9K, 9M, and 9R modules have a second pair of identical optical fiber transmitter andreceiver for redundancy.The optical fiber sizes supported include 50/125 μm, 62.5/125 μm and 100/140 μm for 10 Mbps. The fiber optic port isdesigned such that the response times will not vary for any core that is 100 μm or less in diameter, 62.5 μm for 100 Mbps.For optical power budgeting, splices are required every 1 km for the transmitter/receiver pair. When splicing optical fibers,the diameter and numerical aperture of each fiber must be the same. In order to engage or disengage the ST type connec-tor, only a quarter turn of the coupling is required.CAUTIONCAUTION
