QUALITY MANAGEMENT
EARTHING SYSTEM
Doc No: L&T / PT&D / LE-160666 /
Rev. No.: 0
WP-ELECT / ETG / 03
L&T Construction
PROJECT : IPDS-KANPUR, UP
Page 1 of 11
PROCEDURE FOR INSTALLATION OF EARTHING
Rev No Prepared By Reviewed By Approved By
0
Tarun Kumar M.Manickavasagam M.J.Sebastian
QUALITY MANAGEMENT
EARTHING SYSTEM
Doc No: L&T / PT&D / LE-160666 /
Rev. No.: 0
WP-ELECT / ETG / 03
L&T Construction
PROJECT : IPDS-KANPUR, UP
Page 2 of 11
REVISION CONTROL SHEET
Rev.
Date Details of Revision Prepared By Reviewed By Approved By
No.
0 26-12-2016 INITIAL ISSUE Surajit Das M.Manickavasagam M.J.Sebastian
QUALITY MANAGEMENT
EARTHING SYSTEM
Doc No: L&T / PT&D / LE-160666 /
Rev. No.: 0
WP-ELECT / ETG / 03
L&T Construction
PROJECT : IPDS-KANPUR, UP
Page 3 of 11
CONTENTS
Sl. No. Description Page No.
1 Cover Sheet 1
2 Revision Control Sheet 2
3 Contents 3
4 Scope 4
5 Purpose 4
6 Reference Documents 4
7 Responsibility 4
8 Pre-requisites 5
9 Equipment’s & Accessories 5
10 Procedure 6
11 Acceptance Criteria
12 Records 12
13 Distribution 12
QUALITY MANAGEMENT
EARTHING SYSTEM
Doc No: L&T / PT&D / LE-160666 /
Rev. No.: 0
WP-ELECT / ETG / 03
L&T Construction
PROJECT : IPDS-KANPUR, UP
Page 4 of 11
1. SCOPE:
It covers the installation of earthing system consists of earthing mat, different types of
earth pits at the project of IPDS-Kanpur, UP.
2. PURPOSE:
This is to provide documented procedure for installation of installation of earthing
system.
3. REFERENCE DOCUMENTS:
a) REC/Technical Specifications
b) Approved Vendor Drawings
c) Approved Survey Drawings
d) Approved Pre Shutdown Survey if required
e) Approved Pre Task Plan if required
f) Procedure for Excavation
g) Procedure for Concreting if applicable
h) Procedure for Brick masonry if applicable
i) Procedure for Backfilling
j) Procedure for structural steel fabrication and fillet welding
k) IS 3037
l) EHS plan.
m) Climate information from meteorological department.
n) QMS Manual
4. RESPONSIBILITY:
Responsibility of implementation of this Procedure lies with Project Manager.
5. PRE-REQUISITE:
a. Approved Pre Shutdown Survey shall be available at location if required
b. Approved Pre Task plan shall be available at location if required.
c. Approved Survey Drawing shall be available at the location
d. Inspected materials in good condition shall be available at the location.
QUALITY MANAGEMENT
EARTHING SYSTEM
Doc No: L&T / PT&D / LE-160666 /
Rev. No.: 0
WP-ELECT / ETG / 03
L&T Construction
PROJECT : IPDS-KANPUR, UP
Page 5 of 11
e. All work permits shall be obtained before stating of work.
f. Pep talk on the activity shall be given to the working crew
g. Location specific emergency plan shall be made available to the crew leader,
frontline supervisor and the engineer in charge.
h. Approved FQAP and Checklist for the procedure shall be available at the
location with crew leader, frontline supervisor and the engineer in charge.
i. Qualified Welder
j. Qualified Workmen
k. PPEs & First Aid Kit.
6. EQUIPMENT AND ACCESSORIES:
a) Ladders for pole erection
b) 25mm PP Ropes
c) Electrician tools box
d) insulated Crow bar & spade with wooden handle
e) Trolley/ handcart for manual shifting of materials.
f) Road safety gadgets (Road safety cone, barricading tape, red & green flag
and whistle).
g) Manila Rope, Measuring Tape
h) Concrete material if required
i) Plumb
j) Welding machine, Grinding machine, Buffing machine, pre heating oven,
wire brushes.
k) Welding cable holder, chipping hammer, welding helmet etc.
l) Approved electrodes.
Special tools required for shutdown works
a) Telescopic Discharge Rods with spike
b) Induction Tester(Non Contact Voltage Tester)
c) Clamp meter for earth resistance measurement
d) Temporary earthing system – safety grounding jumpers
QUALITY MANAGEMENT
EARTHING SYSTEM
Doc No:L&T / PT&D / LE-160666 /
Rev. No.: 0
WP-ELECT / ETG / 03
L&T Construction
PROJECT : IPDS-KANPUR, UP
Page 6 of 11
e) Lock and tag for LOTO.
7. PROCEDURE:
The object of an earthing system is to provide as nearly as possible a surface under
and around a station which shall be at a uniform potential and as nearly zero or
absolute earth potential as possible.
The purpose of this is to ensure that, in general, all parts of apparatus other than live
parts, shall be at earth potential, as well as to ensure that operators and attendants
shall be at earth potential at all times. Also by providing such an earth surface of
uniform potential under and surrounding the station, there can exist no difference of
potential in a short distance big enough to shock or injure an attendant when short-
circuits or other abnormal occurrences take place.
7.1. Installation
Earthing Conductor will be as per approved lay out drawing and technical speciation.
Earthing Conductor will be free from pitting, laminations, rust, scale and other Electrical
mechanical defect.
Earthing Conductor will be made straight before installation.
Earthing Conductor to be cut by cutting machine or hand held hack saw and exposed
part will be painted with cold galvanized paint.
Hole shall be done by drilling machine and exposed part will be painted with cold
galvanized paint.
All Earthing Conductor joint shall be welded/Bolted as per approved drawing
All hardware used for Earthing Conductor installation shall be as per REC/technical
specification.
The parts to be welded/bolted shall be cleaned to make them free of oxides, grease, oil,
dirt or any foreign material either by wire brush or by use of cleaner.
The surface to be welded shall be held in position and bind with C-clamp.
The surfaces to be joined shall be overlapped twice the width of the earthing conductor
for straight through joint.
Welding will be done using Electrode of approved by MVVNL.
Burrs, will be removed from the surface & extra deposit will be removed.
On completion of installation continuity of each conductors and all joint shall be
checked.
Black Bitumen will be applied on the surface of Joints & heat affected areas to protect
the joint from rusting.
Where ever earthing conductor run blow ground level, procedure shall be followed as
per specifications.
All Electrical equipment/metal parts of electrical system earthed by means of Earth flat
or as per approved drg.
QUALITY MANAGEMENT
EARTHING SYSTEM
Doc No:L&T / PT&D / LE-160666 /
Rev. No.: 0
WP-ELECT / ETG / 03
L&T Construction
PROJECT : IPDS-KANPUR, UP
Page 7 of 11
Earthing conductor will be fixed to the equipment using Nut Bolt.
Bimetallic strip shall be used for Jointing two dissimilar materials
Contact surface will be cleaned prior to the connection and same will be tighten with
torque Wrench.
Identification of different type of earthing shall be done.
Laying of Earthing Conductor at different medium
7.2.1. Cable tray:
In Cable tray Earthing Conductor shall run in cable tray collar and shall be fixed
using Nut Bolt. The coupling joint will be surmounted by creating upset.
GI stripe will be bolted at least at three minimum positions to the full length cable
tray.
Nut bolt shall be tightened up to the required torque depending upon the size of
the bolt and base metal.
Overlapping of the stripe shall be twice the width of the of the stripe
7.2.2. Panels and cubicle:
Earthing of panels and equipment shall be done by using raiser connected to the
main earth conductor, of adequate size as per approved drawing.
Raiser shall be fixed to the panel using nut bolt with required torque.
7.2.3. Floor and walls
GI earthing stripe shall be fixed using stripe saddle of adequate size on floors walls
and beams.
All Earth conductors are running along with Columns, wall etc shall be supported
by welding / cleating at interval of 1000 mm and 750 mm respectively.
7.2.4. Earthing of Poles
All metal parts of electric pole shall be earthed with electrode type earthing
as per specifications. (20mm dia 2500mm long earthing rod and
6SWG GI wire)
The poles on both sides of railway, telecommunication, road, drain &
river crossing and the poles on which transformer is instal led shall
be earthed as per Specifications.
7.2.5. Switch yard
QUALITY MANAGEMENT
EARTHING SYSTEM
Doc No:L&T / PT&D / LE-160666 /
Rev. No.: 0
WP-ELECT / ETG / 03
L&T Construction
PROJECT : IPDS-KANPUR, UP
Page 8 of 11
The earth mat shall be as per the approved layout. The earth mat shall be formed
with the earthing conductor as per drawing/specifications buried in the ground
at a depth of 750mm.
The earth mat shall extend over the entire switchyard as per the layout.
All the junctions of the steel flats while forming the earth mat and taking risers
from the earth mat for giving earth connections to equipment, steel structures,
conduits cable sheaths shall be properly welded. All joints shall be provided with
suitable angle pieces for proper contact between flats.
Provisions shall be made for thermal expansion of the steel flats by giving smooth
circular bends. Bending shall not cause any fatigue in the material at bends.
The earth mat shall be formed by welding 50x8 mm steel flat to the 100 x 16mm
peripheral earth conductor.
The grounding grid shall be spaced as per drawing/specifications that is in
longitude transverse directions. After the completion of earth mat, the earth
resistance shall be measured.
In case the earth resistance is more than one ohm/specified the earth mat shall
be extended by installing extra electrodes, so that the earth resistance is less than
one ohm/specified.
All fence corner posts and gate posts shall be connected to the ground by
providing suitable size of earth conductor near the posts and connected to the
main grounding mat.
All paint enamel and scale shall be removed from surface of contact on metal
surface before making ground connection.
The risers taken along the main switchyard structures and equipment structures
(up to their top) shall be clamped to the structures at an interval of not more than
one meter.
Grounding electrodes of 32mm dia 2.5mtr. long MS rods shall be provided at the
peripheral corners of the earth mat.
The grounding rods the size as per drawing/specifications shall be driven into
the ground and their tops shall be welded to clamp and the clamp together with
the grounding rods shall be welded to the ground mat.
Lightening arrestors shall be provided with earth pits near them for earthing.
7.3. EARTH PIT
Activity wise work procedure will be as following.
Determine the position of the earth pit as per approved drawing.
Check the resistivity of the soil.
Note down the value
QUALITY MANAGEMENT
EARTHING SYSTEM
Doc No:L&T / PT&D / LE-160666 /
Rev. No.: 0
WP-ELECT / ETG / 03
L&T Construction
PROJECT : IPDS-KANPUR, UP
Page 9 of 11
If the resistivity of the soil is above 20 Ohm meter/drawing/specifications the
earth pit shall be treated with salt and charcoal.
7.3.1. EARTH PIT FOR SWITCH YARD.
Where ever it is specified Cast iron pipes or as per drawing/specifications
125mm dia and 2.75 meters long and 9.5mm thick shall be buried vertically in
the pits and a mixture of Bentonite compound with Black cotton soil a ratio of 1:6
is to be filled 300 mm dia and the pipe for the entire depth.
Where it is not possible to go to a depth of 2.75 meters, 1.3 x 1.3 MMS plates,
25mm thick shall be buried vertically in pits of 2 meters depth and surrounded
by Bentonite mixture at least 2 meter away from any building or structure
foundation. The plates shall be at least 15 meters apart. These earth pits in turn
shall be connected to the earth mat.
7.3.2. PIPE EARTHING
Mark the position of the earth pits as per approved drawing.
The minimum distance between two earth pits shall be double the length of the
earth Electrode. Ensure the same from approved drawing.
Dig the earth pit with manual excavator at the position specified in the approved
drawing.
The depth of the earth pit shall be below the permanent moisture level.
The size of the pit for pipe earthing shall be diameter of the hole shall be 300 mm.
The hole should be of uniform diameter from top to bottom
Insert the electrode vertically in to the hole.
Compact the soil.
Connect the funnel at the top of the earth electrode by welding
Connect the earthing strips to the earth electrode.
Check the tightness of the nuts at joints and verify the continuity of the earhting
loop.
7.3.3. PLATE EARTHING
Mark the position of the earth pits as per approved drawing.
The minimum distance between two earth pits shall be double the length of the
earth Electrode. Ensure the same from approved drawing.
Dig the earth pit with manual excavator at the position specified in the approved
drawing.
The depth of the earth pit shall be below the permanent moisture level.
QUALITY MANAGEMENT
EARTHING SYSTEM
Doc No:L&T / PT&D / LE-160666 /
Rev. No.: 0
WP-ELECT / ETG / 03
L&T Construction
PROJECT : IPDS-KANPUR, UP
Page 10 of 11
The size of the pit for plate earthing shall be 1.5M*1.5M*3M.
Assemble the plate earth system as per specifications.
Insert the plate earth system vertically in to the pit.
Compact the soil.
Connect the funnel at the top of the earth electrode by welding
Connect the earthing strips to the earth electrode.
Check the tightness of the nuts at joints and verify the continuity of the earthing
loop.
7.3.4. CHEMICAL PIPE EARTHING:
Chemical pipe earthings are generally used for earthing of equipments at 33/11KV
Substations.
The hollow pipe used in the chemical pipe earthing is fitted with a G.I. strip 40x6mm and
CCM (Crystalline conducive mixture) is compressed in to the pipe and pipe is sealed at
both the end. CCM is a semi metal and the hollow pipe filled with CCM behave like a salt
pipe and therefore the current carrying capacity increases substantially.
7.4. TREATING THE EARTH PIT
If the resistivity of the soil where the earth pit has to be installed is more than 20
Ohm meter/ drawing/specifications the earth pit shall be treated with salt and
charcoal.
For treated earth pit only one third of the excavated soil shall be kept for refilling.
The rest shall be replaced by equal amount of salt and charcoal. The soil, charcoal
and salt are used in equal layers of 150 mm for refilling of treated earth pit.
If the moisture level is very low, the bentonite powder shall be used for treating
the pit.
7.5. Maintenance free earth pit
The maintenance free earth pit shall be installed as per manufacturer instructions.
7.6. Construction of Earth Pit chamber:
Earth pit chamber shall be constructed by using RCC/BRICK wall as specified in
the approved drawing
It shall be covered with CI cover
Proper nomenclature and identification mark shall be done
QUALITY MANAGEMENT
EARTHING SYSTEM
Doc No: L&T / PT&D / LE-160666 /
Rev. No.: 0
WP-ELECT / ETG / 03
L&T Construction
PROJECT : IPDS-KANPUR, UP
Page 11 of 11
Test point shall be installed inside the chamber at convenient position.
8. RECORD
Checklist for Fabrication
Welding and Painting Inspection Report
Checklist for earthing
9. DISTRIBUITION
Distribution shall be as per contractual specification with controlled copy only.
1) Master Copy with Project Manager
2) Controlled copy to Planning Manager
3) Controlled copy to Section InCharge
4) Controlled copy to QA/QC & QMS - Cluster
