Relays for high-tension lines

The author considers the following arrangements desirable: For radial feeders not in parallel — inverse-time-limit overload relays, with selective ground relays. Radial feeders in parallel — reverse-power relays in combination with reverse-time-element relays, or the balanced system. Single lines in tandem — definite and inverse-time-limit relays with progressively longer time settings near the generating station. Two or more parallel lines in tandem — inverse-time-limit relays at the points where the power leaves the station or substation, and overload relays in combination with reverse-power relays at the points where the power enters the substation; also, the balanced system preferable, when possible. Single line ring systems — inverse-time-limit relays, combined with reverse-energy relays, or, preferably, the balanced system. Parallel line ring systems — inverse-time-limit relays on the outgoing feeders at the generating stations, and a balanced interconnected combination of reverse-energy and inverse-time-limit relays at the receiving ends of the supply feeders. Tie lines — some balanced arrangement. Generator relays seldom used, but arrangements are suggested. Transformers — differential relays. Special grounding relays for extra high-tension cable feeders. Appendices A, B, C describe connections of reverse-power relays, relay testing and a special installation.