BS7430 CODE OF PRACTICE FOR EARTHING PDF
resistance to earth of a plate R in ohms (code of practice earthing history First published as CP First published as BS BS Code of practice for protective earthing of electrical installations. 16/22 Total Solution to Earthing & Lightning Protection | 9AKKA Technical BS Code of practice for protective earthing of electrical.
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Your basket is empty. Table 1 gives examples of resistivity only. Chemical treatment of soil has environmental implications and should not be considered as a long term solution in order to meet a specified level of resistance, apart from the risk of corrosion to the earthling system. However, onsite resistivity testing should always be carried out prior to carrying out an earth prachice design and installation.
Take the smart route to manage medical device compliance. Overview Product Details What is this standard about? The resistance R should be taken as the ratio of the voltage between the inner electrodes and the current between the outer electrodes.
The value of resistance required might not always be amenable to an automatically set value. It may be considered necessary to apply numerical pracrice which are more complex than the formulae given below and software is available to carry out the more detailed calculations. You may experience issues viewing this site in Internet Explorer 9, 10 or It is important to ensure that their resistance areas do not overlap.
It also includes some technical changes to correct and clarify formulae and equations. A waterlogged location is not essential unless the soil is sand or gravel. 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.
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.
Measurements and Calculations Of Earth Electrode Systems (BS ) | EEP
For conventional sizes, the resistance is approximately inversely proportional to the linear dimensions, not to the surface areai. Earthing systems should consist of copper conductors, copper clad or austenitic steel rods of appropriate dimensions, cast iron plates, or praactice piles used individually or connected together in combination to form a single local earth electrode system.
The resistance to earth of concrete encased steelwork or of concrete reinforcing pracitce varies according to the type of soil, its moisture content, and the design of the foundation. They may be used to give an indication of the difficulties that one might face in preparing an adequate design at the chosen earthig. The total electrode area formed by the underground metalwork of large structure may often be used to provide an earth resistance lower then that obtainable by other methods.
Customers who bought this product also bought BS EN It includes a number of editorial changes which clarify practiec meaning of the text and corrects values and symbols. Accept and continue Learn more about the cookies we use and how to change your settings.
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.
The content is copyrighted to EEP and may not be reproduced on other websites. Leave a Comment Click here to cancel reply. It is of particular relevance to: The resistivity so determined applies to an electrode separation distance a, which is related to the depth of investigation.
BS +A Code of practice for protective earthing of electrical installations
When two or more strips in straight lengths, each of length L in meters m and a separation distance s metres are laid parallel to each other and connected together at one end only the combined resistance may be calculated from the following equation:. A possible source of such current might be incompatibility with other buried metalworkincluding other types of earth electrode to which foundation metalwork may be bonded. This situation is unlikely to arise if the electrode has a resistance sufficiently low to avoid dangerous voltages to 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.
This model is more closely aligned to the basic theory behind the electrostatic behaviour of earrthing earthing system componentin effect stating more clearly the interactive effect of the value of s which for practical purposes has long been set as being not less than twice the depth of the rod.
This is one of the best design reference i have seen. 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.