The fiber coming in from outside and the one coming in from the relay gets spliced inside a fiber distribution panel. See video below on how fiber gets spliced. The one shown in the GIF image comes with up to 144 count fiber. From relaying standpoint only 2 fibers are needed (1-TX, 1-RX) for each relay. An OPGW cable contains a tubular structure with one or more optical fiber in it, surrounded by layers of steel and and aluminium wires. The conductive part of the cable serves to bond adjacent towers to earth ground, and shields the h. CT and PT wiring in a conventional substation using copper wires. A digital substation using fiber-optic cables for communication digitizes data related to the. At the electrical substation, the demand for “smart grid” technologies using Ethernet-based automation processes is transforming operations, enabling faster and more reliable power conversion, transmission and distribution systems. OPGW cables are installed on transmission and distribution power lines, above the high-voltage power conductors since acts as the protection from lightning strikes. OPPC. This document is for Relevant Electrical Standards document only.