By and large electrical switch gear is named as low voltage switch gear up to 1KV. The term LV switch gear includes low voltage circuit breakers, switches, off-load electrical isolators, HRC wires, earth leakage electrical switches, miniature circuit breakers (MCB) and shaped case circuit breakers (MCCB) etc. for example each A projected jewel to protect the LV framework. The most popular use of LV switch gear is in LV distribution boards. The following are the parts of this framework.
Incomer:
The earner takes care of getting close to the power capacity of the revenue transport. The switch gear used in the earner should have a basic exchange gadget. Switch gear gadgets connecting to the incomer should be equipped to withstand odd currents for short unambiguous periods to allow the downstream gadgets to function. Be that as it may, this deficiency created in the framework should be the link of the greatest value obstacle of the present. It should have an interlocking game plan with downstream gadgets. For the most part air circuit breakers are ideally used as interrupters on gadgets. A low voltage air electrical switch is ideal for this reason as a result of its accompanying highlights.
1. Straightness.
2. Effective implementation.
3. The High normal current rating up to 600 A.
4 .High short circuit withstand limit up to 63 kA.
Despite the fact that air circuit breakers have long stumbling time, enormous size, significant expense yet they are generally reasonable for low voltage switch gear for the previously mentioned highlights.
Sub – Incomer:
The next downstream part of the LV dispersion board is sub-income. These sub-revenues draw power from primary revenue transport and supply this capacity to feeder transport. Gadgets introduced as part of sub-income should have the following elements.
1. Capacity to accomplish economy without forfeiting security and well-being
2. Need for generally less number of interlocking since it cover restricted are of organization.
Capacity to accomplish economy without forfeiting security and well beingNeed for generally less number of interlocking since it cover restricted are of organization.
Feeders:
1. Engine Feeder
The engine feeder should be protected against overload, cut-off, current up to locked rotor condition and single staging.
2. Advanced Hardware Burden Feeder.
3. Modern hardware loads connected to the feeder like broiler, electroplating shower etc. are generally protected by MCCBl and switch meld dis connector units.
4. Lighting Burden Feeder.
5. It is as safe as a modern hardware load but additional ground spillage current protection is provided for this situation to reduce any damage to life and property that may occur from unsafe spread of current and fire.
In the framework of LV switch gear, electrical equipment is protected from short-out and overload conditions by means of electrical wires or electrical switches. Be that as it may, the human administrator is not sufficiently protected against errors within the machines. This problem can be solved by using an earth spillage electrical switch. It operates at low spillage current. The earth spillage electrical switch can detect spillage currents as low as 100 mA and is suitable for machine isolation of less than 100 mcc.
The typical diagram of low voltage is switchgear is shown above. Here the main revenue comes from the LV side of the electrical transformer. An MCCB (not shown in figure) along with an electrical isolator feeds this incomer bus. Two sub-inputs are connected to the incomer bus and all these inputs are protected by either a switch fuse unit or an air circuit breaker. These switches are connected to the bus section switch or bus coupler in such a way that only one incomer switch can be turned on if the bus section switch is in the ON position and both sub incomer switches can be turned on only if the bus The section switch is in the off position. This arrangement is useful to prevent any mismatch of phase sequence between sub-income earners. Different load feeders are connected to either side of the feeder bus. Here the motor feeder is protected by a thermal overload device with a conventional switch fuse unit. The heater feeder is only protected by a conventional switch fuse unit. Household lighting and AC loads are protected separately by small circuit breakers with a typical conventional switch fuse unit. This is the most basic and simplest scheme for low voltage switchgear or LV distribution board.
