Feeder protection cable feeders and overhead lines

This chapter presents feeder protection cable feeders and overhead lines. Translay is a voltage balance system. Solkor unit protection is used where solid metallic pilot wires are available. The system is a differential protection system and is available as Solkor R/Rf. Optional equipment includes pilot wire supervision and injection intertripping systems. The relays incorporate diodes, which act as switches and permit the use of a single pilot loop for two-way signaling using a system of time sharing switched at the power frequency. A distance relay, as its name implies, has the ability to detect a fault within a preset distance along a transmission line or power cable from its location. Every power line has a resistance and reactive per kilometer related to its design and construction, so its total impedance will be a function of its length or distance. A distance relay therefore looks at current and voltage and compares these two quantities on the basis of Ohm's law. The chapter explains tripping characteristics, application onto a power line, effect of load current, effect of arc resistance, and different shaped characteristics.