Brief description of switch yard
Bus Bars
An electrical bus bar is defined as a conductor or a group of conductor used for collecting electric power from the incoming feeders and distributes them to the outgoing feeders. In other words, it is a type of electrical junction in which all the incoming and outgoing electrical current meets. Thus, the electrical bus bar collects the electric power at one location.
The bus bar system consists the isolator and the circuit breaker. On the occurrence of a fault, the circuit breaker is tripped off and the faulty section of the bus bar is easily disconnected from the circuit.
The electrical bus bar is available in rectangular, cross-sectional, round and many other shapes.
The rectangular bus bar is mostly used in the power system. The copper and aluminum are used for the manufacturing of the electrical bus bar.
The various types of bus bar arrangement are used in the power system. The selection of the bus bar is depended on the different factor likes reliability, flexibility, cost etc. The following are the electrical considerations governing the selection of any one particular arrangement.
· The bus bar arrangement is simple and easy in maintenance.
· The maintenance of the system did not affect their continuity.
· The installation of the bus bar is cheap.
The small substation where continuity of the supply is not essential uses the single bus bar. But in a large substation, the additional bus bar is used in the system so that the interruption does not occur in their supply.
Circuit breakers
A circuit breaker is a switching device that interrupts the abnormal or fault current. It is a mechanical device that disturbs the flow of high magnitude (fault) current and in additions performs the function of a switch. The circuit breaker is mainly designed for closing or opening of an electrical circuit, thus protects the electrical system from damage. All high-voltage circuit breakers may be classified under two main categories i.e oil circuit breakers and oil-less circuit breaker.
Lighting arrestor
The device which is used for the protection of the equipment at the substations against travelling waves, such type of device is called lightning arrester or surge diverter. In other words, lightning arrester diverts the abnormal high voltage to the ground without affecting the continuity of supply. It is connected between the line and earth, i.e. in parallel with the equipment to be protected at the substation.
Location of Lightning Arrester
The lightning arrester is located close to the equipment that is to be protected. They are usually connected between phase and ground in an AC system and pole and ground in case of the DC system. In an AC system, separate arrester is provided for each phase.
In an extra-high voltage AC system the surge diverter is used to protect the generators, transformers, bus bars, lines, circuit breakers, etc. In HVDC system the arrester is used to protect the buses, valves converter unit, reactors, filter, etc.
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