The power system deals with voltage above 36KV, is regarded as high voltage. Since the voltage level is high, the arcing formed during switching operation is also quite high. Therefore, special care is to be taken during the designing of high voltage switchgear. High voltage circuit breaker is the major component of HV switchgear, thus high voltage circuit breaker ought to have special features for reliable and safe operation. Switching operation and faulty tripping of high voltage circuit are very rear. At time these circuit breakers remain, at ON state, and might be operated after a long period of time. Thus CBs must be dependable enough to make sure of safe operation, as when necessary. High voltage circuit breaker technology has changed drastically in the last 15 years.
SF6 circuit breaker, air blast circuit breaker and minimum oil circuit breaker are mostly used for high voltage switchgear. Vacuum circuit breaker is hardly used for this purpose since till date vacuum technology is not sufficient for interrupting very high voltage short circuit current. There are two kinds of SF6 circuit breaker, that is, single pressure SF6 breaker and two pressures circuit breaker. Single pressure system is the latest and updated high voltage switchgear system, these days. Nowadays SF6 gas as arc quenching medium has become most accepted for high and extra high voltage electrical power system. Though, SF6 gas has strong influence on the greenhouse effect. It has 23 times stronger influence on the greenhouse effect, than that of CO2. Therefore, leakage of SF6 gas in the service life of circuit breaker should be prevented. For minimizing the emission of CF4 – SF6, N2 – SF6 and SF6 gas mixture, might be used in circuit breaker in future, as an alternate of pure SF6. It should always be taken into consideration that, no SF6 gas comes out in atmosphere throughout the maintenance of CB.
Switch boards, comprising the Main LV switch board, also known by the acronym MLVS are vital to the dependability of electrical installation. It must act in accordance with the set guidelines that govern the construction and design of LV switch gear congregations.
A switchboard is the point at which an incoming power supply segregates into separate circuits, each of that is controlled and protected by the switchgear or fuses of the switchboard. Switchboard is partitioned into a couple of functional units, comprising all the mechanical and electrical elements that contribute to the fulfillment of a given purpose. It symbolizes a key link in the constancy chain.
Therefore, the type of switchboard should be perfectly modified to its application. Switchboard Manufacturers must note that the construction and design must comply with working practices and applicable standards.
The switchboard enclosure offers dual protection:
- Security of switchgear, indicating relays, fusegear, instruments, etc. against vibrations, mechanical impacts and various other external influences are prone to interfere with operational integrity (dust, EMI, vermin, moisture, etc.)
- The defense of human life against the possibility of direct and indirect electric shock.
Modern industrial switchboards are sternly fabricated with metal enclosed design construction; no energized parts are easy to get while the panels and covers are closed. Earlier, open switchboards were made with switches and several other devices were mounted on panels fabricated of ebony, granite or slate asbestos board. Metal enclosure of switchboard is linked to earth ground for personnel protection. Large switchboards might be unattached floor mounted enclosures with stipulation for incoming connections at the top or bottom of the enclosure. Switchboard may perhaps have incoming bus duct or bus bars for the source connection and for large circuits fed from the board. Switchboard might include a control or metering compartment estranged from the power distribution conductors.
Electrical Substation, a part of an electrical transmission, distribution and generation system’s main concern is encountering is its cost and reliability. An apt design attempts to strike a balance between the two sub stations, to attain reliability without a high cost. The design must also allow growth of the station, whenever obligatory.
Selection of the location of Electrical Substations must consider a lot of factors. Adequate land area is obligatory for installation of equipment with obligatory clearances for electrical protection, and for access to preserve large electrical machines like transformers. Where the land is expensive, like in urban areas; gas insulated switchgear may perhaps save money. The location or the spot must have room for expansion because of the load growth or premeditated transmission additions. Ecological effects of the substation should be considered, like, road traffic, noise and drainage effects. Earthing or grounding system ought to be designed. The total ground probable rise, and the gradients in probable throughout the fault (known as “touch” and “step” potentials), have got to be calculated to defend passers-by throughout the short-circuit in the transmission system. The substation locations have got to be rationally central to the distribution area to be provided. The location should be secure from intrusion by passers-by, together with protecting people from harm by arcs or electric shock, and to defend the electrical system from disoperation because of vandalism.
The primary step in planning a substation layout is the planning out of one line diagram that shows in simplified form the switching and protection requisite display and the incoming supply lines and transmission lines or outgoing feeders. It is a general practice by several electrical utilities to chart out one-line diagrams with principal elements, such as, switches, lines, transformers, circuit breakers set on the page similarly to the way the apparatus would be laid in the definite station.