Following is a picture showing the earthing busbar of a main switchboard. Below the picture is a simple performance specifications for the grounding of the switchboard.
The are also two more posts on switchboard installation check and switchboard electrical tests. The latter is a general list of tests and inspections that are usually required of a major switchboard such as main switchboards and large subswitchboards.
Photo 1 - Earthing busbar of a main switchboard (MSB)
The earthing of an electrical switchboard shall be in accordance with BS 7430, and the color coding of protective conductors shall be in accordance with IEC 60646.
Switchboard earthing busbar
The switchboard earthing busbar shall be installed internally along the full length of the switchboard. The material of the busbar shall be the same as the material of the phase busbars. (See more photos: Switchboard earthing busbar.)
Equipment earth bar
Where the substation consists of 11 kV switchgears, transformers and LV switchboards, earthing copper tape shall be installed continuously along the full length of the substation.
It shall be connected to the main system earth bar at both ends using appropriate size earthing bolts with nuts and spring washers.
The earthing copper tape shall be made of hard-drawn high conductivity copper.
The cross-section of the earth bar shall be sufficient to carry the rated short-time withstand current of the switchgear for the allowable temperature rise and the time specified.
Internal branch earth connections
The branch earth connections made from the switchboard earthing busbar to the individual switchboard components shall consist of adequately sized copper strips, or green/ yellow striped PVC sheathed stranded copper conductor.
The termination lugs shall be of the compression type.
Earthing of metal parts
All metal parts of a switchboard where live components (such as relays, instruments, indicating lights etc) are mounted shall be earthed through branch connections to the switchboard earthing busbar.
Doors of the switchboard shall also be similarly earthed.
Frames of the draw-out circuit breakers shall be connected to the earthing busbar through a substantial plug type earthing contact.
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