Friday, 22 May 2015

Earthing guideline for hazardous area

Earthing guideline in hazardous area
Earthing is required for –
·         Safety of working personnel
·         Equipment safety
·         Protection against fault

earthing in hazardous location

Size of earth conductor
Type of equipment
Earth conductor size
Street light poles
10 mm dia solid GI wire rope
Motor upto 3.7KW
8 SWG solid GI wire
Motor upto 5.5KW to 30KW & welding receptacle
10 mm dia solid GI wire rope
Motor above 37KW including HT motor
16 mm dia solid GI wire rope / 40mm x5 mm GI strip
Building columns
40mm x 5 mm GI strip
Storage tank vertical or horizontal
40mm x 5 mm GI strip
Loading racks
40mm x 5 mm GI strip
Pipe racks, heat exchanger, Vessel
40mm x 5 mm GI strip
Small equipments and instruments
8 SWG solid GI rope
Lighting, power and instrument panel
10 mm dia solid GI wire rope
Main earth bus /MV &HV switchgear interconnection /power transformer
As per calculation
EHV/HV substation
As per calculation
Push button station
8 SWG solid GI wire
Bonding of pipe
25 mm2 insulated flexible copper cable
Lighting transformer
16 mm dia solid GI wire rope
1. Earth connections to individual equipment from nearest earth plate/ grid may also be done alternatively using Aluminum/ Copper conductor PVC insulated core of size not less than half the cross-section of respective power cable to the equipment (Motor, Panel etc.). Connections shall be made using crimped type of lugs.
2. Earth rods and conductors shall be designed to cope with the conditions imposed. The earth conductor shall be adequately sized to carry the applicable maximum earth fault current without undue temperature rise. All joints shall be protected against corrosion.
3. All the electrical equipment operating above 250 volts shall have two separate and distinct connections to earth grid.
4. Lighting Fixtures shall be earthed through the extra core provided in the lighting cable.

5. The cross sectional area of earthing conductor shall be minimum 4 sqmm.

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