Switchboards Explained


Switchboards are basically a distribution board (DB) that receives a large amount of power and dispatches it in small measures to various electrical equipment located within the power distribution system. In addition, switchboards have power-controlling devices such as breakers, switches, and protection devices such as fuses.

switchboards are generally divided into the following four classes:

  • Direct-control panel-type
  • Remote mechanical-control panel-type
  • Direct-control truck-type
  • Electrical-operated

Direct-Control Panel-Type switchboards

With the direct-control panel-type, switches, rheostats, bus bars, meters, and other apparatus are mounted on the switchboard or near the switchboard. The switches and rheostats are operated directly by operating handles specifically if they are mounted on the back of the board. For both AC and DC, voltages are limited to 600 V or lower, but with oil circuit breakers, they may operate up to 2500 V. These types of switchboard panels are not recommended for capacities of more than 3000 kVA.

Remote Mechanical-Control Panel-Type switchboards

Remote mechanical-control panel-type switchboards are the AC switchboards with the bus bars and connections removed from the panels and mounted separately away from the load. The oil Circuit Breakers are operated by levers and rods. This type of switchboard is designed for a heavier duty than the direct-control type switchboards and as a result can be used for up to 25 000 kVA.

Direct-Control Truck-Type switchboards

Direct-control truck-type switchboards are used for 15 000 V or lower and consist of equipment enclosed in steel compartments completely assembled. The high-voltage parts are enclosed and the equipment is interlocked to prevent any operational mistakes. This type of a switchboard is designed for low- and medium-capacity plants and for auxiliary power in large generating stations.

Electrically Operated switchboards

Electrically operated switchboardsemploy solenoid or motor-operated circuit breakers. Rheostats are controlled by small switches mounted on the switchboard panels. Electrically operated switchboards make it possible to locate high-voltage and other equipment independent of the location of the switchboard.

These switchboards should be erected at least 1-2 m (3-4 feet) from the walls. Switchboard frames and structures should be grounded. For low-potential equipment, the conductors on the rear of the switchboard are usually made of a flat copper strip known as a copper bus bar. Aluminum bus bars are also used due to its low cost. This type of switchboard should be individually adapted for each specific electrical equipment/system.