Electrical switchgear is a term that comprises of all the switching devices related with mostly the power system protection. Switchgears in substations are situated on both the low voltage and high voltage side of large power transformers. The switchgear on the lower voltage side of the transformers may perhaps be located in the building, with medium voltage circuit breakers for distribution circuits, all along with protection, control and metering equipment.
Medium Voltage Switchgear Application
An arc furnace is necessary to get switch off and on often. The current to be switched might be from 0 to 8 times of the rated current of the furnace. An arc furnace is be switched on and off at its normal rated current up to 2000A, approximately 100 times per day. A normal, oil, air or SF6 circuit breaker is not at all reasonable for this frequent operation. Typical vacuum circuit breaker is most suitable alternative for this frequent high current circuit breaker operation.
One more application of medium voltage switchgear is single phase railway track system. The major function of the circuit breaker is linked with railway traction system, is to disrupt short circuit, on the overhead catenary system that come about frequently and are transitory in nature. Thus circuit breaker used for this purpose must have, short breaking time for short arcing time, small contact gap, VCB and quick breaking is the best probable solution. In fact arcing energy is much higher in the single phase CB than 3 phases CB. It is much lesser in circuit breaker than that in usual circuit breaker. The number of short circuit takes place in the overhead catenary system much higher than those occurring on electrical transmission system. The medium voltage switchgear possessed with vacuum circuit breaker is most appropriate for traction application.