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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
Sr.no.
Type of equipment
Earth conductor size
1
Street light poles
10 mm dia solid GI wire rope
2
Motor upto 3.7KW
8 SWG solid GI wire
3
Motor upto 5.5KW to 30KW & welding receptacle
10 mm dia solid GI wire rope
4
Motor above 37KW including HT motor
16 mm dia solid GI wire rope / 40mm x5 mm GI strip
5
Building columns
40mm x 5 mm GI strip
6
Storage tank vertical or horizontal
40mm x 5 mm GI strip
7
Loading racks
40mm x 5 mm GI strip
8
Pipe racks, heat exchanger, Vessel
40mm x 5 mm GI strip
9
Small equipments and instruments
8 SWG solid GI rope
10
Lighting, power and instrument panel
10 mm dia solid GI wire rope
11
Main earth bus /MV &HV switchgear interconnection /power transformer
As per calculation
12
EHV/HV substation
As per calculation
13
Push button station
8 SWG solid GI wire
14
Bonding of pipe
25 mm2 insulated flexible copper cable
15
Lighting transformer
16 mm dia solid GI wire rope
General:
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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