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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Second important characteristic of earthing connection is earthint it MUST be capable of carrying the maximum expected fault current. Therefore, the various factors which affect the resistance to earth and fault current capacity of the buried conductor, designated the earth electrode, should be considered.
Table 1 gives examples of resistivity only.
Measurements and Calculations Of Earth Electrode Systems (BS ) | EEP
Above ground and at anchor bolts it may generally done by attaching a bond conductor to bypass each structural joint. It should be noted that these types of measurement are not always simple and can often result in a wide range of resistance values depending upon a number of factors such as those mentioned in above paragraph. This is a amendment to a British Standard on how to meet UK electrical installation earthing requirements.
Most first approximation formulae are related to homogenous soil, which is rarely the case in practice, where the different layers of strata will affect the distribution of current passing through the electrode.
It is important to ensure electrical continuity between all metalwork considered to be part of the electrode. Find Similar Items This product falls into the following categories. It is essential to measure the resistance to earth of any metalwork it is intended to use as an electrode, and to monitor its value at regular intervals afterwardsin order to confirm that it continues to provide an adequate connection to earth.
The purpose of earthing System earthing involves the provision of a connection to the general mass of earth. Thus a pipe rod or strip has a much lower resistance than a plate of equal surface area. This requires careful assembly during installation to ensure that the bottom of the plate is resting in the medium used and not on the chalk or high resistivity substrata.
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.
Effective earthing safeguards people from the risk of electric shock. 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.
Earthing systems should consist of copper conductors, copper clad or austenitic steel rods of appropriate dimensions, cast iron plates, or steel piles used individually or connected together in combination to form a single local earth electrode system.
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. Alternating current should not be expected to cause corrosion, but, rectification sufficient to produce a very small proportion of direct current might take place.
It also includes some technical changes to correct and clarify formulae and equations. The resistivity found applies to soil depth a, so by repeating the measurement with different values of athe average resistivity to various depths may be found and the results indicates whether any advantage is to be gained by installing deeply driven electrodes eaarthing order to reach strata of a lower resistivity.
Measurements of the soil resistivity for the pre-determination of the resistance to earth or the impedance to earth should be carried out using a four probe method widely known as the Wenner method as follows.
This section deals only with a straight run of conductor. Customers who bought this product also bought BS EN These figures are very general and should not be used to replace actual measurements made at the proposed site.
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Chemical treatment of soil has environmental implications and should not be considered as a long term solution darthing order to meet a specified level of resistance, apart from the risk of corrosion to the earthling system.
The connecting strip to the above ground disconnection point should be fully insulated to avoid electrolytic action. It is important that consideration is given to the possibility of corrosion of the metalwork reinforcement.
Current should be passed between the two outer electrodes and the resistance R may be found as the ratio of the esrthing between the inside electrodes to the current conducted through the outside electrodes.
In particular, continuous earth currents should earthibg given attention. It is therefore important to recognize this issue if a long horizontal tape or bare cable is being considered for producing a low earth resistanceeven though the impedance will ultimately be limited to a final value see Figure 4. This applies particularly to surfaces which might have been primed before assembly. This should include the size earthihg shape of the earth conductor, the resistivity of the soil in which it is buried and the connection of the system to it.
For conventional sizes, the resistance is approximately inversely proportional to the linear dimensions, not to the surface areai.
Melvin Surita Mar 07, Connections to the plate should be by copper conductor, welded, riveted or otherwise attached with material that will not cause corrosion at the joint. This model is more closely aligned to the basic theory behind the electrostatic behaviour of an 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.
It may be considered necessary to apply numerical methods which are more complex than the formulae given below and software is available to carry out the more detailed calculations. Search all products by. They may be used to give an indication of the difficulties that one might face in preparing an adequate design at the chosen location. Premium Membership Premium membership gives you an access to specialized technical articles and extra premium content electrical guides and software.