The term switchgear, used in association with the electric power system, or grid, refers to the combination of electrical disconnects, fuses and/or circuit breakers used to isolate electrical equipment. Switchgear is used both to de-energize equipment to allow work to be done and to clear faults downstream. This type of equipment is important because it is directly linked to the reliability of the electricity supply.
Power distribution substations have to handle high voltages. High voltage indoor switchboards are generally installed in the switch rooms of the substations. The switchgear distributes power at various voltage levels. Switchgear contain a lot of insulated conductors like busbars. The insulations used in the modern day switchboards can be either condenser can be either condenser type where insulation is made of either synthetic resin bonded paper (SRBP) and conducting aluminium foil in alternating layers or cast resin encapsulated type where cast resin is used instead of SRBP.
Frequent flash over in switchgear requires expensive repairs and leads to power outage resulting in huge losses in revenue. Power distribution substations have to handle high voltages. High voltage indoor switch boards are generally installed in the Switch Rooms of the substations. The switchgears distribute power at various voltage level.
Condenser type: This type of insulation is generally made from synthetic resin bonded paper (SRBP) and conducting aluminum foil in alternating layers. The paper, usually used in condenser type insulation, is highly hygroscopic, and thus absorbs moisture from the surrounding air. This leads to the degeneration of the insulation with time, as is evident by the increase in Tan Delta (loss angle) values. This results in failure of the insulation as well as in a flashover and, ultimately in the failure of the switchgear itself.
Cast resin encapsulated type : Alternatively, cast resin component is also used for insulation instead of SRBP. In this case moisture makes the dust inside the switch room to become sticky and settle over the switch gears. This leads to severe electrical insulation problem and failure.
Insulating sleeve type: In case of insulating sleeve, the high humidity along with dust lead to surface tracking and thus, cause a flashover.
Humidity control by dehumidifying such switch rooms ensures that the insulating components do not fail as it eliminates flashover in the case of SRBP insulation, and in the case of cast resin or insulated sleeve insulation, dehumidification keeps the dust dry so that it can be wiped off easily from time to time.
Most switchgear rooms are non air conditioned. However, the current trend indicates that more and more switch gear rooms with hi-tech, state-of-the art PCB controlled switchgears are air-conditioned as the sophisticated controls of the switchgear need temperature control also.