Functions Performed by Electrical Switchgear
Functions Performed by Electrical Switchgear (on photo Blokset switchboard withdrawable unit/cassette)

Electrical Switchgear

National and international standards define the method for making electrical distribution circuits as well as the purpose and functions of switchgear. There are three main functions, namely:

  1. Circuit protection takes three main fault types into account:
    1. Overloads,
    2. Short-circuits (Both of which adversely affect the lifetime of cables and loads)
    3. Insulation faults, harmful for persons and equipment.
  2. Isolation is used to separate a circuit or a device from the remainder of the installation to allow 100% safe operation,
  3. Control allows the user to take voluntary action on installation operation:
    1. When such action takes place in normal operating conditions (on load, with no overcurrent) in order to energise or de-energise all or part of the installation, control is said to be “functional”,
    2. When such action is essential (whatever the load condition of the installation) in order to immediately de-energise all or part of the installation, control is said to be of the “emergency stop” kind.

Three main functions of electrical circuits:

  1. Protection,
  2. Isolation,
  3. Control,

The switch is used for:

  1. Control,
  2. Often isolation.

For protection it must be combined with:

  1. Circuit-breaker,
  2. Fuses,
  3. Residual current device (if necessary).

A variety of switchgear perform all or some of these three main functions. The following table situates the role of the main switchgear:

Functions perfomed ProtectionsIsolationControl
FuseYes (3)YesNoNoNo
SwitchNoNoYes? (1)(2)Yes?Yes
Disconnector – fuseYesYesNoYesNo
Switch – fuseYesYesYes? (1)(2)Yes?Yes
ContactorNoNoNo NoYes
Circuit-breakerYesYesYes? (2)Yes?Yes

Yes –  Basic function of the switchgear considered (always performed)
Yes? –  Additional function possible (not always performed)

(1) Possible with a switch with automatic opening.
(2) Possible with addition of a “Residual Current Device (RCD)“.
(3) gG fuse only

Resource // Schneider Electric – Low voltage switches

About Author //


Edvard Csanyi

Edvard - Electrical engineer, programmer and founder of EEP. Highly specialized for design of LV high power busbar trunking (<6300A) in power substations, buildings and industry fascilities. Designing of LV/MV switchgears.Professional in AutoCAD programming and web-design.Present on


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  2. ashafa
    Oct 29, 2015

    informative….very helpful

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    Nov 15, 2014

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