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 LV switchboards

Switchboards are situated at the node points in a system for the connection and disconnection of parts of the system, and for their selective protection. In an electrical installation system they have the further purpose of conveying the electrical energy supplied by the electricity supply authority through cables, for example, to the main substation to distribution transformers and, if necessary, to further subsidiary substations.

Note: Metal-enclosed Switchgear is surrounded by a metal case or housing, usually grounded.

Switchboard with withdrawable equipment comprise a number of adjacent switchboard sections housing circuit breakers or mechanical switches which are fitted with isolating contacts, the opening of which establishes an isolating distance.

Metal-clad Switchgearis a specific type of metal-enclosed switchgear. While all metal-clad switchgear is metal-enclosed, not all metal-enclosed switchgear can be classified as metal-clad. Metal-clad is characterized by always having the following features:

• The main switching and interrupting device is removable (drawout), with a mechanism to move it between connected and disconnected positions, and equipped with self-aligning and self-coupling primary disconnecting devices and disconnectable control wiring connections.

• All live parts are enclosed within grounded metal compartments.

• Automatic shutters that cover primary circuit elements when the removable element is in the disconnected, test or connected positions.


• Mechanical interlocks are provided for proper operating sequence under normal operating conditions.