A panel earthing strip is the copper or GI bar that runs along a switchboard as the earth busbar, bonding every metal part and tying the panel back to the earth grid. It is sized to the panel fault level, usually 25 x 6 mm for distribution boards up and 50 x 6 mm or larger for main panels.
Sizing the panel earth strip
Size it to carry the panel short-circuit current for the breaker clearing time, using the IS 3043 rule - see the earthing strip size chart and current-carrying-capacity guide. Copper is preferred inside panels for its conductivity and compactness.
How it connects
- Every door, gland plate and mounting bonds to the earth bar with a strip or braid.
- The earth bar runs the full width and lands on two earth terminals.
- Both terminals connect to the external earth grid with separate strips.
- Joints are bolted with spring washers and an anti-oxidant paste.
