Fuses may used both in low voltage and high-voltage lines.A fuse is a non-adjustable, direct-acting, single-phase device that responds to both the magnitude and duration of current flowing through it.Isolators on the line side of the line circuit breakers should equipped with grounding blades. However, these are capable of dealing with small charging currents. Under loaded conditions and for this reason, interlocked with circuit breakers to prevent operation on load.Isolators help to have a sectionalized bus system.Isolators also used for disconnecting lines and allow the equipment to taken out of the system for repair, maintenance, and testing.They are provided for isolating all circuit breakers for maintenance and repair.
TRANSMISSION SUBSTATION COMPONENTS MANUAL
An isolator is a manual or motor operated disconnect switch.Isolators used for isolating the circuit when the current has already interrupted.The trip circuit actuated by one or more relays that sense the abnormal condition.In the event of any abnormal situation, the movable contact of each pair made to open against spring forces by a mechanical device through a trip circuit energized by a battery. Under the normal operating condition, the contacts of each pair close on themselves, and the circuit breaker said to closed.A circuit breaker is a device that can interrupt a section or a circuit automatically if an abnormal or faulty condition exists in that section.An instrument transformer used for metering and protection.Power Transformers: Step-up transformers used at generating stations to step up the voltage for transmission, whereas step-down transformers used at receiving end stations to step down the voltage for secondary transmission, and primary and secondary distribution.The transformer can be classified into two kinds: It used to transform power from one voltage level to another voltage level without changing the frequency. Outdoor bus bars are widely spaced to prevent birds with a large wing spread causing short circuits of the buses.Outdoor bus bars are generally mounted horizontally insulated from the earth by post insulators made of porcelain.The materials normally use for bus bars are copper and aluminum.An electric bus collects electric energy at one location and the bus bar is the conductor through which the current flows.Bus, therefore, refers to the main collectors of electrical energy which may be bars, rods, tubes, or channels. The term ‘bus’ is derived from the word omnibus which means a collector of things.