Electric earthing pdf

This is why we need Electrical Earthing or Grounding in electrical installation systems. Below are the basic needs of Earthing. Earthing is not done anyhow. A complete electrical earthing system consists on the following basic components. That part of the earthing system which interconnects the overall metallic parts of electrical installation e. The resistance of the earth continuity conductor is very low.

Size of the Earth Continuity Conductor or Earth Wire depends on the cable size used in the wiring circuit. The cross sectional area of the Earth Continuity Conductor should not be less than the half of the cross sectional area of the thickest wire used in the electrical wiring installation. Generally, the size of the bare copper wire used as earth continuity conductor is 3SWG. Earthing lead is the final part of the earthing system which is connected to the earth electrode which is underground through earth connecting point.

There should be minimum joints in earthing lead as well as lower in size and straight in the direction. Generally, copper wire can be used as earthing lead but, copper strip is also used for high installation and it can handle the high fault current because of wider area than the copper wire.

A hard drawn bare copper wire is also used as an earthing lead. In this method, all earth conductors connected to a common one or more connecting points and then, earthing lead is used to connect earth electrode earth plat to the connecting point. To increase the safety factor of installation, two copper wires are used as earthing lead to connect the device metallic body to the earth electrode or earth plate. It should not be considered that the two earth leads are used as parallel paths to flow the fault currents but both paths should work properly to carry the fault current because it is important for better safety.

The size or area of earthing lead should not be less than the half of the thickest wire used in the installation. The earth lead connection methods is shown in the above fig. Note: We will post additional article about Earth Plate size with simple calculations… Stay tune.

A metallic electrode or plate which is buried in the earth underground and it is the last part of the electrical earthing system. In simple words, the final underground metallic plate part of the earthing system which is connected with earthing lead is called earth plate or earth electrode.

A metallic plate, pipe or rode can be used as an earth electrode which has very low resistance and carry the fault current safely towards ground earth. Both copper and iron can be used as earthing electrode. The size of earth electrode In case of copper.

In case of Iron. It is recommended to bury the earth electrode in the moisture earth. If it is not possible, then put water in the GI Galvanized Iron pipe to make possible the moisture condition. In the earthing system, put the earth electrode in vertical position underground as shown in the above fig. This action makes the possible increase in the size of the earth electrode which leads a better continuity in the earth earthing system and also helps to maintain the moisture condition around earth plate.

Good to know:. Since, the water level is different in the different areas; therefore, the depth for earth electrode installation is also different in various areas. But, the depth for earth electrode installation should not be less than 10ft 3 meter and should below 1 foot Motors , Generator , Transformers etc should be connected from to earth electrode two different places.

The metallic pipe should be 2 meter below from the surface of ground. To maintain the moister condition, put 25mm 1inch coal and lime mixture around the earth plate. For effectiveness and convenience, you may use the copper rods We will discuss the installation method of rod earthing latter. Earthing can be done in many ways.

The various methods employed in earthing in house wiring or factory and other connected electrical equipment and machines are discussed as follows. In plate earthing system, a plate made up of either copper with dimensions 60cm x 60cm x 3. For proper earthing system, follow the above mentioned steps in the Earth Plate introduction to maintain the moisture condition around the earth electrode or earth plate.

A galvanized steel and a perforated pipe of approved length and diameter is placed vertically in a wet soil in this kind of system of earthing. It is the most common system of earthing. The size of pipe to use depends on the magnitude of current and the type of soil. The dimension of the pipe is usually 40mm 1.

The moisture of the soil will determine the length of the pipe to be buried but usually it should be 4. A copper rod of The length of embedded electrodes in the soil reduces earth resistance to a desired value. In this method of earthing, the waterman Galvanized GI pipes are used for earthing purpose. Make sure to check the resistance of GI pipes and use earthing clamps to minimize the resistance for proper earthing connection. If stranded conductor is used as earth wire, then clean the end of the strands of the wire and make sure it is in the straight and parallel position which is possible then to connect tightly to the waterman pipe.

In this method of earthing, strip electrodes of cross-section not less than 25mm x 1. If copper with a cross-section of 25mm x 4mm 1in x 0. If at all round conductors are used, their cross-section area should not be too small, say less than 6.

The length of the conductor buried in the ground would give a sufficient earth resistance and this length should not be less than 15m. The usual method of earthing of electric equipments, devices and appliances are as follow:. Various specifications in respect to earthing as recommended by Indian Standards are given below.

Here are few;. As emphasized on earlier, earthing is provided in order. However, if excessive current is not earthed, appliances will be damaged without the help of fuse in place. You should note that excessive current are earthed at their generating stations which is why earth wires carries very little or no current at all. It therefore implies that it is not necessary to earth any of the wires live, earth and neutral wires contained in a PVC.

Earthing the live wire is catastrophic. I have seen a person killed simply because a live wire got cut from overhead pole and fell to the ground while the ground was wet.

Excessive current is earthed at generating stations and if at all the earthing is not efficient due to fault, earth fault interrupters will be there to help. Fuse help only when the power transmitted is above the rating of our appliances, it blocks the current from reaching our appliances by blowing off and protecting our appliances in the process.

In our electrical appliances, if excessive currents are not earthed, we would experience severe shock. Earthing takes place in electrical appliances only when there is a problem and it is to save us from danger. If in an electronic installation, a metallic part of an electrical appliance comes in direct contact with a live wire that results from maybe failure of installation or otherwise, the metal will be charged and static charge will accumulate on it.

If you happen to touch the metallic part at that moment you will be zapped. But if the metallic part of the appliance is earthed, the charge will be transferred to earth instead of accumulating on the metallic part of the appliance. In addition, if a live wire touches accidentally in a faulty system to the metallic part of a machine. Now, if a man touches that metallic part of the machine, then the current will flow through their body to the ground, hence, he will get shocked electrocuted which may lead to serious injuries even to death.

To be continued…. Thanks for share great info with us. I will recommend you to prefer plate earthing than pipe earthing. Plate earthing is the best earthing. Outstanding blog, covering almost everything about the types of earthing!

The importance of earthing, its types and fuse is very well explained. Manufacturers recommendations should be sought with regards to connections to earth electrodes. With TT, the consumer must provide their own connection to earth, i. Requirements of BS Earth electrodes BS recognises a wide variety of types of earth electrode. Regulation lists the types recognised which include earth rods, earth plates and. The soil resistivity of the ground is probably the single most important factor in the determination of the type of earth electrode.

Rods can only be as effective as the contact they make with the surrounding material. Thus, they should be driven into virgin ground, not disturbed backfilled ground. Where it is necessary to drive two or more rods and connect them together to achieve a satisfactory result, the separation between rods should be at least equal to their combined driven depth to obtain maximum advantage from each rod.

In some locations low soil resistivity is found to be concentrated in the topsoil layer, beneath which there may be rock or other impervious strata which prevents the deep driving of rods, or a deep layer of high resistivity.

Only a test or known information about the ground can reveal this kind of information. In such circumstances, the installation of copper earth tapes, or pipes or plates, would be most likely to provide a satisfactory earth electrode resistance value. Whatever form an earth electrode takes, the possibility of soil drying and freezing, and of corrosion, must be taken into account.

Preferably, testing of an earth electrode should be carried out under the least favourable conditions, i. Further information on earthing principles and practice can be found in BS : Code of Practice for Earthing. Earthing conductors Earthing conductors which are defined in BS as a protective conductor connecting the main earthing terminal of an installation to an earth electrode or other means of earthing must be adequately sized particularly where buried partly in the ground, and be of suitable material and adequately protected against corrosion and mechanical damage.

The size of an earthing conductor is arrived at in basically the same way as for a circuit protective conductor, except that Table 54A of BS must be applied to any buried earthing conductor. Sizing of circuit protective conductors There are several factors which may influence or determine the size required for a circuit protective conductor.

A minimum cross-sectional area of 2. An example would be a bare or insulated copper conductor clipped to a surface, run on a cable tray or fixed to the outside of a wiring enclosure. Such a circuit protective conductor must also be suitably protected if it is liable to suffer mechanical damage or chemical deterioration or be damaged by electrodynamic effects produced by passing earth fault current through it. If mechanical protection is not provided the minimum size is 4 mm2 copper or equivalent.

BS provides two methods for sizing protective conductors including earthing conductors see also Table 54A. The easier method is to determine the protective conductor size from Table 54G but this may produce a larger size than is strictly necessary, since it employs a simple relationship to the cross-sectional area of the phase conductor s.

The second method involves a formula calculation. The formula is commonly referred to as the adiabatic equation and is the same as that used for shortcircuit current calculations see Regulation It assumes that no heat is dissipated from the protective conductor during an earth fault and therefore errs on the safe side.

Even so, application of the formula will in many instances result in a protective conductor having a smaller csa than that of the live conductors of the associated circuit. This is quite acceptable. Regulation states: The cross-sectional area, where calculated, shall be not less than the value determined by the following formula or shall be obtained by reference to BS I is the value in amperes rms.

Account shall be taken of the effect, on the resistance of circuit conductors, of their temperature rise as a result of overcurrent - see Regulation The advantage of this system is that it provides an effective and reliable method of providing customers with an earth connection.

For example the maximum Ze specified by a distributor is 0. However, under certain supply system fault conditions PEN conductor of the supply becoming open circuit external to the installation a potential can develop between the conductive parts connected to the PME earth terminal and the general mass of earth. However, since there are multiple earthing points on the supply network and bonding is provided within the building complying with BS , the risk is considered to be small.

Whilst PME systems provide an effective and reliable earth connection. For example Regulation 9 4 of the Electricity Safety, Quality and Continuity Regulations does not allow the combined neutral and protective conductor to be connected electrically to any metalwork in a caravan or boat.

This prevents PME terminals being used for caravans or boat mooring supplies, although they may be used for fixed premises on the sites, such as the site owners living premises and any bars or shops, etc. Petrol filling stations are another area where precautions need to be taken. The reference publication is Guidance for the design, construction, modification and maintenance of petrol filling stations, published by the Association for Petroleum and Explosives Administration APEA and the Institute of Petroleum, which recommends a TT supply for hazardous areas.

A separate earth electrode and RCD or other alternative arrangement is required to ensure the segregation of petrol filling area earthing and that of the PME earth of the distribution network. A PME earth may be used for permanent buildings such as shops and restaurants. Also, mines and quarries are another area. A supply taken to an underground shaft, or for use in the production side of a quarry, must have an earthing system which is segregated from any system bonded to the PME terminal.

Finally, because of the practical difficulties in bonding all accessible extraneous-conductive-parts electricity distribution companies might not provide a PME earth to agricultural and horticultural installations and construction sites. The circumstances in which a distributor will not provide a means of earthing for the consumer are usually where the distributor cannot guarantee the earth connection back to the source, e.

A distributor also might not provide means of earthing for certain outdoor installations, e. The electricity distributor is required to make available his supply neutral or protective conductor for connection to the consumers earth terminal, unless inappropriate for.

Construction site, farm or swimming pool installations might be inappropriate unless additional precautions are taken, such as an additional earth electrode. In such situations the usual form of system earthing is TN-S. Open navigation menu. Close suggestions Search Search. User Settings.

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