Earthing strip size and fault level typical

EQUIPMENT EARTHING

All the equipment should be grounded with double run earth strip directly connected to earth mat at two different points.  The table provides the guidelines for Selection of Cross section of Earth conductor as per IEEE 80-2000 Clause 11.3.1 Equation 37 & Mild Steel as an Earth Conductor.

earthing strip size

Sr.	Fault current Level (KA)	Minimum Required Area of Cross Section (Sq.mm)
1	5	54
2	10	108
3	15	163
4	20	217
5	25	271
6	30	325
7	35	379
8	40	433

For various Equipments such as Power Transformer, Station Transformer, 11 KV Switch gear, 415V Panel, Light panel, Junction box, Street Lighting pole, Metallic fence, Isolator, Gantry tower & Electronic Earthing different cross sections of Earth conductor shall be selected as per the fault level. For switch gear rooms, a local earth conductor of adequate size of G.I flat may be run around the room below floor level to facilitate earthing of equipments in switchgear room.