<P> In a common design, incoming lines have a disconnect switch and a circuit breaker . In some cases, the lines will not have both, with either a switch or a circuit breaker being all that is considered necessary . A disconnect switch is used to provide isolation, since it cannot interrupt load current . A circuit breaker is used as a protection device to interrupt fault currents automatically, and may be used to switch loads on and off, or to cut off a line when power is flowing in the' wrong' direction . When a large fault current flows through the circuit breaker, this is detected through the use of current transformers . The magnitude of the current transformer outputs may be used to trip the circuit breaker resulting in a disconnection of the load supplied by the circuit break from the feeding point . This seeks to isolate the fault point from the rest of the system, and allow the rest of the system to continue operating with minimal impact . Both switches and circuit breakers may be operated locally (within the substation) or remotely from a supervisory control center . </P> <P> With Overhead Transmission Lines (OHTLs), the propagation of lightning and switching surges can cause insulation failures into substation equipment . Line entrance surge arrestors are used to protect substation equipment accordingly . Insulation Coordination studies are carried out extensively to ensure equipment failure (and associated outages) is minimal . </P> <P> Once past the switching components, the lines of a given voltage connect to one or more buses . These are sets of busbars, usually in multiples of three, since three - phase electrical power distribution is largely universal around the world . </P> <P> The arrangement of switches, circuit breakers, and buses used affects the cost and reliability of the substation . For important substations a ring bus, double bus, or so - called "breaker and a half" setup can be used, so that the failure of any one circuit breaker does not interrupt power to other circuits, and so that parts of the substation may be de-energized for maintenance and repairs . Substations feeding only a single industrial load may have minimal switching provisions, especially for small installations . </P>

Name any five substation components and state their function