Construction Safe Work Method

Earthing System Method Statement and Procedure

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Earthing or grounding purpose is to connect electrical conductors to the earth. Earthing system carries the current or electrical fields created around the structures or electrical devices to the ground.

Why do we need earthing?

  • Protect personnel against electrical hazards like electric shock and electrocution
  • Safeguards protect electrical devices, appliances, power tools, machinery etc. from current leakage
  • Damage from lightning to structures, installations and the entire electric system by using Lightning Arresters.
  • Prevents fire in the electrical systems
  • Avoids interference with communication circuits

What are earthing system types

Different types of earthing systems are available. Popular methods are:

  • Plate Earthing: A copper plate or galvanized plate is buried in an earth pit below ground level. The plate electrode connects the electrical conductors to the earth.
  • Pipe Earthing: A galvanized steel perforated pipe inside the ground connects the electrical conductors to the earth.
  • Rod Earthing: Similar to the Pipe earthing. A copper rod replaces the pipe electrode.
  • Chemical earthing: Similar to the pipe earthing. A chemical compound material replaces the charcoal and salt layers.

This article presents detailed work method statement and procedure of these earthing systems

The choice of earthing method primarily depends on:

  • Service continuity requirement at different voltages
  • Safety requirements for humans and equipment
  • Possibility of overvoltage
  • Maintenance requirements
  • Cost consideration

Purpose of this Method Statement

This method statement describes the procedure and resources required to do the work. Use any other resources and methods not referred to in this method statement to suit the project requirement. Always execute the work safely complying with the required standard.

This method statement summarizes suggested method of executing works safely within any constraints. This method statement offers advice and guidance to the personnel involved in this activity to:

a) Carry works in a manner that’s safe at all times;

b) Know the hazards involved in the activity;

c) Ensure controls to steer clear of hazard exposure are in place.

The sequence of activities is a repetitive process and many aspects are common to distinct sites. Include with detail, any crucial aspects specific to the project. Always follow the approved checklists prior to the start of the activity.

What this Method Statement covers

The scope of this document covers:

  • A safe work method for carrying out Earthing work
  • Work procedure for different types of earthing
  • Materials, equipment, and tools needed to carry out the earthing work
  • Applicable standards throughout the execution of the earthing system work

Applicable Standards

IS : 2309-1989 [Indian Standard for Protection of Buildings and Allied Structures against Lightning]

IS : 3043 Indian Standard Code of Practice for Earthing

Indian Electricity Rules 1956

Central Electricity Authority Regulations (CEAR)

Relevant regulations of the electric power supplying authority

Materials, Equipment, and Tools

  • Meggar for Earth resistivity testing
  • Welding toolkit
  • Excavator for earth pit excavation
  • Copper wire or strip
  • GI or Copperplate
  • Pipe/Rod
  • Coke/Charcoal and Salt
  • PVC Wires
  • Cement
  • Bricks
  • Funnel
  • Wire mesh

Health, Safety, and Environment

Execute all activities with due regard to Health, Safety & Environment of all the employees and third parties.

  • Assess for any underground and overhead electrical lines or some other obstructions
  • Carry the work under the strict guidance and supervision
  • Maintain adequate visibility at all times by providing appropriate lighting
  • Report immediately any anomaly found in the components

Personal Protective Equipment (PPE)

Safety Helmet
Safety Helmet

Safety Footwear
Safety Footwear

Safety Glasses
Safety Glasses

Safety Gloves
Safety Gloves

Refer to the Standard Operating Procedure (SOP) for Personal Protective Equipment (PPE) for more details.

Quality

  • Make all arrangements as per the approved shop drawing.
  • Check all materials and fittings for quality and standards compliance.
  • Store materials according to the manufacturer instructions.
  • Check all connections for cleanliness, continuity and an appropriate amount of tightness.
  • Make sure the specifications of components match with that specified in the approved shop drawing.
  • As per IS : 3043, all earth connections shall be visible for inspection.
  • Earthing system installation shall enable testing of each earth electrode.
  • Conducts all required tests and submit the results for approval.

Procedure for plate earthing

Plate earthing diagram
Plate electrode earthing system
  • Earth pit: Excavate and make an earth pit of size 900 mm x 900 mm x minimum 3.0 meter deep. Level the bottom surface.
  • Plate electrode: Use GI plate of minimum size 600 Mm x 600 Mm x 6.3 mm thickness. In case of a Copperplate, a minimum thickness of 3.15 mm can be used.
  • Earthing connection: Fix two numbers of 50 mm x 6 mm GI strips to GI plate firmly with GI nut, check nut, bolt, and washer with each strip fixed to GI plate at two locations. Weld the GI strips to GI plate. Join the two strips at the top with a GI strip of the same size. Any loose earthing connection with the earth plate will have an adverse effect on the electrode system resistivity.
  • Water connection: Fix a 25 mm diameter GI pipe attached at the top with a funnel covered with wire mesh. Water poured through this pipe will keep the area surrounding the earth plate moistened.
  • Backfill the excavated pit with soil free of stones and lumps.
  • Inspection chamber: Construct brick chamber of size 450 x 450 x 450 mm with 100 mm thick brick walls over a P.C.C. layer. Keep 100 mm of the chamber above ground level. Cover the top with a cast iron (CI) cover.
  • Follow the approved design and drawing for fixing and laying of earth wires or GI/copper strips between the earth electrode and the electrical room.

Suggested item description for G.I. Plate earthing:

Supply and erection of G.I. plate earthing with earth plate size 600X600X6.3 mm, at least 3.0 meter below ground with double G.I. strip 50 x 6 mm bolted to the plate, 25 mm dia GI pipe with wire mesh funnel for watering, 230 brick masonry inspection chamber of size 450 mm x 450 mm x 450 mm, C.I. cover 300mm x 300mm (10 Kg) complete with necessary length of double G.I. earth wire no. 6 SWG bolted with lug to the plate and covered in 12 mm dia G.I. pipe 3.0 meter long complete connected to the nearest switchgear with end socket and duly tested by earth tester and recording the results. Excavation work is included in the scope of the contractor. Job to be executed as per approved drawing and technical specifications and as directed by Engineer Incharge complete.

Procedure for pipe or rod electrode earthing

Pipe electrode earthing
Pipe earthing system
  • Make a borehole of 500 mm diameter and 3.5 meters deep or as per the approved design and drawing.
  • Lower the Pipe electrode made of a 65 mm diameter GI perforated pipe of 3.0-meter length attached at the top with a funnel covered with wire mesh. A G.I. strip is fixed to the electrode to act as an earthing connection. For rod earthing, a copper rod of required diameter is used in place of the pipe.
  • Fill the annular space between the electrode and borehole walls with alternating layers of coke or charcoal and common salt.
  • Inspection chamber: Construct brick chamber of size 450 x 450 x 450 mm with 100 mm thick brick walls over a P.C.C. layer. Keep 100 mm of the chamber above ground level. Cover the top with a cast iron (CI) cover.
  • Follow the approved design and drawing for fixing and laying of earth wires or GI/copper strips between the earth electrode and the electrical room.

Suggested item description for G.I. Pipe electrode earthing:

Supply and erection of G.I. earth pipe electrode 65 mm diameter, at least 3.0 meter below ground with 40 Kg alternate layers of charcoal and salt with and with wire mesh funnel for watering, 230 brick masonry chamber (450 mm x 450 mm x 450 mm), C.I. cover 300mm x 300mm (10 Kg) complete with necessary length of double G.I. earth wire no. 6 SWG bolted with lug to the plate and covered in 12 mm dia G.I. pipe 3.0 meter long complete connected to the nearest switchgear with end socket and duly tested by earth tester and recording the results. Excavation work and making borehole are included in the scope of the contractor. Job to be executed as per approved drawing and technical specifications and as directed by Engineer Incharge complete.

Procedure for chemical earthing

Chemical earthing procedure is similar to the pipe electrode system. A chemical compound is used in place of alternate charcoal or coke and salt backfill material. The chemical compound eliminates the necessity of moistening the backfill by water pouring as in the case of conventional pipe electrode system. Due to this reason, chemical earthing is free of maintenance.

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