BS Code of practice for protective earthing of electrical installations. BS EN Earthing of power installations exceeding 1kVac. – BS Code of practice for protective earthing of electrical installations. – BS Code of. A well designed earthing system is basic for any electrical installation to avoid the systems”. Great Britain: BS “Code of practice for Earthing”. France: NF.
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Professional in AutoCAD programming. To obtain a low overall resistance the current density should be as low as possible in the medium surrounding the electrode. You may experience issues viewing this site erthing Internet Explorer 9, 10 or In the case of contacts between metalwork within concrete or below ground, such as reinforcing bars, this may best be effected by welding.
Search all products by. Leave a Comment Click here to cancel reply. These figures are very general and should not be used to replace actual measurements made at 74300 proposed site. In high resistivity locations or on rocky ground where long term performance is required, it may be considered necessary to utilize a conductive concrete to improve earth contact resistance around an earth rod or strip tape where applicable.
This is related to the hemispherical radius of the rod and that has avoided the effects of using less than the two-times constraint in design thinking. earthint
The effective resistivity is also controlled by the mineral salts in the ground and the level of moisture contentwhich is why it should be remembered that readings taken 4730 after installation earhhing vary considerably from the original test results. Where there is an option, a site should be chosen in one of the following types of situations in the order of preference given: Learn more about the cookies we use and how to change your settings.
Effective earthing safeguards people from the risk of electric shock. This connection should have a resistance not greater than that required to operate safety mechanisms to isolate the electricity supply from a fault situation. For conventional sizes, the resistance is approximately inversely proportional to the linear dimensions, not gs the surface areai. Please download Chrome or Firefox or view our browser tips.
However, onsite resistivity testing should always be carried out prior to carrying out an earth system design and installation.
BS +A Code of practice for protective earthing of electrical installations
System earthing involves the provision of a connection to the general mass of earth. You may find similar items within these categories by selecting from the choices below:.
Current should be passed between the two outer electrodes and the resistance R may be found as the ratio of the voltage between the inside electrodes to the current conducted through the outside electrodes.
Wherever significant continuous earth leakage current is expected, it is recommended that a main electrode of the types described in previous section be provided to which the foundation electrodes can be bonded to provide auxiliary electrodes, thus giving assistance to high fault currents. The minimum ground cover should not be less than mm and ideally the surrounding soil should be damp. Click to learn more.
This may be taken as an indication of the possible gain from driving deeper rods, etc. This website is best viewed with browser version of up to Microsoft Internet Explorer 8 or Firefox 3. Table 1 gives examples of resistivity only.
The basic nature and properties of soil in a given location cannot be changed without considerable expense, and careful consideration of the geology should be used to determine the best location for an earthing system.
Soil resistivity may be measured in a similar manner to the establishment of the resistance of the earth electrode.
This applies particularly to surfaces which might have been primed before assembly. The resistance to earth of concrete encased steelwork or of concrete reinforcing bars varies according to the type of soil, its moisture content, and the design of the foundation. Care should be taken to avoid a site where water flows over it e. The purpose of earthing System earthing involves the provision of a connection to the general mass of earth.
This should include the size and shape of the earth conductor, the resistivity of the soil in which it is buried and the connection of the system to it.
Measurements and Calculations Of Earth Electrode Systems (BS ) | EEP
It should be noted that environmental conditions such as temperature have an impact on earth resistivity with a corresponding decrease in resistivity as temperature rises.
Ideally confirmation of the combined resistance of all the electrodes should be obtained, but the earth resistance of a structure covering a large area might be quite low and an accurate measurement on a completed structure might be difficult or impossible to achieve. Other shapes are not covered here. Who is this standard for? Where the plate is placed in a cut out slot, e. It is important that consideration is given to the possibility of corrosion of the metalwork reinforcement.
Allowance should be made for the consequent increase in electrode resistance due to changes in moisture content when using measurements made during the installation of a structure. Soil temperature has some effect on the upper layers of strata, but is only important under frosty conditions. Therefore any part of an electrode system which is less that 0. There are commercially available materials to achieve this effectively, but care should be taken to understand how they work during installation to ensure that they remain in contact with the rod or strip and do not shrink or swell away after drying out.
The effect of other reinforcement which might be attached by wire ties only, may be neglected. The majority of the formulae presented in this section relate to low frequency currents and high frequency examples are not included.
Plates, if used, should be installed as small units of not greater than 1. An earthing system should be of the highest integrity and of robust construction to ensure that it remains safe and will not endanger the health and safety of persons or their surroundings.