Earthing Electrodes – Best Installation Practices

Earthing System is essential for any electrical installation to avoid dangers associated with fault currents and lightning strikes. A properly designed common earthing system is used for both electrical system and lightning protection system. An earthing system comprises of protective earthing conductor, equipotential bonding

bars, connectors and earthing electrode.

1      A good earthing system aims to

2       Protect installations and equipment by providing a low impedance path for fault currents.

3      Ensures that all exposed conductive parts do not reach a dangerous potential.

4       Avoid the risk of fire in electrical installation systems.

5       Provide security for people by limiting step and touch voltages – by providing an alternate path for the fault currents to flow.

6       Provide safe path to dissipate lightning and short circuit currents.

7       Improve the quality of the signal by equal signal reference and minimize the electromagnetic noise.

8      Provide stable platform for operation of sensitive electronic equipments i.e. to maintain the voltage at any part of an electrical system at a known value so as to prevent over current or excessive voltage on the equipment.

Reference Standards

IS 3043 Code of Practice for Earthing.
IEC 62561-1 Lightning Protection System Component -Requirements for Connection Components.

 

IEC 62561-2 Lightning Protection System Component – Requirements for Conductors and Earth Electrodes.
IEC 62561-7 Lightning Protection System Component – Requirements for Earthing Enhancing Compounds.
NBC-2016 National Building Code of India.
IEC 60364-5-54 LV     Electrical     Installations    – Selection     and     Erection     of Electrical Equipment – Earthing Arrangements     and Protective Conductors.

 

 

General

Horizontal ring earthing combined with  vertical  earth electrodes shall be used. This is  called  as Type B earthing in IS/IEC 62305-3, recommended  for installtions with electronics as well as explosive areas. From this combined earth electrodes (ring + vertical electrode) equipotential bonding bars need to be provided to power and signal / communication incoming in the facility. Components need to be used shall be as follows:

 

Earth Electrodes

Horizontal Earth Electrode : Copper coated steel round conductor 10 mm(78 sq mm) solid with a minimum coating thickness of 100 microns shall be used. Horizontal earth conductor shall have minimum number of joints. The minimum length between joints shall be greater than 20 meters.

Installation of Horizontal earth Electrode : Horizontal ring earth electrodes shall be installed as  a  closed loop of 1 meter away from the building at a minimum depth of 500 mm below soil. A 500 mm deep trench shall be excavated and the earth electrode shall be placed in this trench. Joints (exothermic welded) shall

Horizontal Earth Electrode : Copper coated steel round conductor 10 mm(78 sq mm) solid with a minimum coating thickness of 100 microns shall be used. Horizontal earth conductor shall have minimum number of joints. The minimum length between joints shall be greater than 20 meters.

Installation of Horizontal earth Electrode : Horizontal ring earth electrodes shall be installed as  a  closed loop of 1 meter away from the building at a minimum depth of 500 mm below soil. A 500 mm deep trench shall be excavated and the earth electrode shall be placed in this trench. Joints (exothermic welded) shall be made and tested for its strength. Fill the trench with excavated soil after removing stones and other rubbles from the excavated soil. For rocky areas or places with stones, cover the conductor, 100mm around, with Earth enhancing material. Keep it in wet condition for 2 days so that it sets to become concrete, the fill the balance trench with soil without any rubbles.

Fig. 1: Horizontal Conductor in 100 mm Earth Enhancement Material

 

Vertical Earth Electrodes

Driven rod – vertical earth electrodes shall be of copper coated solid steel of 20 mm with a minimum coating thickness of 250 microns. Each electrode shall be 1 meter long with suitable coupling mechanism between the rods so that multiple rods can be driven deep in soil

Augured Hole – Vertical earth electrodes installed inside augured hole shall be of copper coated solid steel of

17.2 mm with a minimum coating thickness of 250 microns. Each electrode shall be 3 meter long.

 

Installation of Vertical Earth Electrodes

Hammering : Earth electrode shall be hammered in the soil. Hammering can be done manually or with an electric hammer. Electrodes shall be connected one above the other and inserted in soil. Minimum number of electrodes shall be 3 meters (3 nos of 1 meter rods). This installation offers better long term performance and can be executed in places with normal soil.

Figure – 2 : installtion of vertical earth electrode – hammering

 

Augured Hole: This installation shall be executed in place where the soil is clay or rocky. Augur a hole of 100 mm dia and 3000 mm deep. Place the electrode in the augured hole. Fill it with earth enhancing material

/ compound (Refer clause – 5.1.3). The hole shall be filled completely with this material. At least 25 kgs of compound is required to fill in each hole.

Figure – 3 : installtion of vertical earth electrode in augured hole

 

 

Chemically Charged Electrode

UL listed chemically charged electrode can be used in places with rocky soil. The chemically charged electrode shall be of 3 metres long, made of copper pipe with a minimum external diameter of 55 mm and wall thickness of 2.5 mm. The chemicals filled inside the charged electrode leaches into the nearby soil and provide a low resistance value. UL listing of the electrode (including drawing in UL certificate) shall be verified before purchase of these rods.

When a single earthing rod provides a poor earth value of more than 10 ohms and if the value is not stable throughout the year, chemically charged electrodes can be used, Installation method shall be as per the manufacturers recommendation in augured hole.

Multiple Earth Electrodes

If one earth electrodes does not provide required value, additional rods shall be installed ideally 2 rod lengths apart, but as a minimum at 1 rod lengths apart. The more electrodes used, better will be the electrical connection to the earth. Install them around the perimeter of your shelter or equipment. Connect all electrodes together with a horizontal earth conductor (5.1.1a) and finally  to the equipotential bonding bar at the shelter’s power entry panel.

Joints in Earth Electrodes

All joints under soil shall be exothermically welded. joints with SS clamps and SS bolts are allowed only in exposed areas.

Earth Enhancing Material

Conductive concrete based earth enhancing materials shall be used for back filling the augured hole after inserting the vertical earth electrode. Approximately 25 kg’s of material shall be used for a 3 meter rod inserted in a 100 mm augured hole in a slurry form. The earth enhancing material shall not contain Bentonite content.

Testing and Approval of Earth Electrodes, Joints, Exothermic welding and Earth enhancing material:- Vertical and horizontal earth electrodes shall be type tested as per IEC 62561 – 2 and joints / conductor fasteners shall be tested as per IEC 62561 – 4 for tensile  strength,  coating  adhesiveness, accelerated

 

Share

Leave comment

Subscribe to our Newsletter!

Sign up to receive environmental news and updates!