Earth electrode

The earth electrode Neutral grounding Substation grounding Supply system grounding Bonding... 

The resistivity of the soil in any particular location will be a function of moisture content, soil temperature and presence of dissolved salts. At a site where climatic conditions vary considerably throughout the year, earth electrodes should be buried at a depth where such changes will not affect the resistivity. Grounding rods are generally made of copper bonded onto a steel core. The copper provides a good connection to earth and offers a high corrosion resistance, while the steel core gives the mechanical... 

The earth electrode system must be designed to be capable of carrying without damage to the full earth fault current of the supply system. 

TT system All exposed conductive parts of an installation are connected to an earth electrode, which is electrically independent of the source earth. 

The connection with earth i i made using earth electrodes at Or near the ter rninal ends. The electrodes may be immersedinthe,sea or buried on land.arid, at one end of the system, the electrode. will be negafive to the surrounding earth. Part of the return current may therefore floW via nearby buried or immersed pipes and cables. 

Submarine ieiecomthunications cables operate at less than 1 A but sub-. marine power cables may operate at several hundreds Of amperes and will require larger spacing between the earth, electrodes and nearby burled or immersed structures. IfpOssible, testsShould be made with trial earth elfec. trOdes at both ends of. the submarine cable and on Off tests made before bringmg the power supply bii the system into permanent Use., ... 

Fig. 2-20. Scheme of a field installation of CHIM 1- current source 2- ore body 3- halo of dispersion 4- host rocks ApAs- element collectors B- auxiliary earth electrode (reproduced with permission from Ryss et al., 1987a). 

A corona discharge is induced upon application of an electric potential of several kV across the electrodes. Ionized molecules from the air are forced by the electric field to move to the surface of the sample. The deposited ions induce image charges on the earthed electrode. Thereby, a static electric field of about... 

This is the type of supply more often found when the installation is fed from overhead cables. The supply authorities do not provide an earth terminal and the installation s circuit protective conductors (CPCs) must be connected to earth via an earth electrode provided by the consumer. lET Regulation 542.2.3 lists the type of earth rod, earth plate or earth tapes recognized by BS 7671. An effective earth connection is sometimes difficult to obtain and in most cases a residual current device (RCD) is provided when this type of supply is used. The arrangement is shown in Fig. 3.36. 

Earth electrodes connected to the earth terminal of an electric fence controller must be separate from the earthing system of any other circuit and should be situated outside the resistance area of any electrode used for protective earthing. The electric fence controller and the fence wire must be installed so that they do not come into contact with any power, telephone or radio systems, including poles. Agricultural and horticultural installations should be tested and inspected in accordance with Part 6 of the Wiring Regulations every three years. 

Low-voltage supplies having earthing arrangements which are independent of the supply cable are classified as TT systems. For this type of supply it is necessary to sink an earth electrode into the general mass of earth, which then forms a part of the earth return in conjimction with an RCD. 

Disconnect the installation protective equipotential bonding from the earth electrode to ensure that the test current passes only through the earth electrode. 

Using a line earth loop impedance tester, test between the incoming line conductor and the earth electrode. 

The lEE Guidance Note 3 tells us that an acceptable value for the measurement of the earth electrode resistance will be about 200 Q, or less. 

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