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.
|Published (Last):||24 July 2014|
|PDF File Size:||12.43 Mb|
|ePub File Size:||8.31 Mb|
|Price:||Free* [*Free Regsitration Required]|
To design, specify, inspect and periodically test and maintain earthing systems without endangering those who come into contact with them, users need to follow the guidelines and recommendations outlined in this standard.
It is also essential to consider the current density at the surface of the earth electrode and the ground potentials in its vicinity. Find Similar Items This product falls into the following categories. The standard is earthng in the following sectors: Alternating current should not be expected to cause corrosion, but, rectification sufficient to produce a very small proportion of direct current might take place.
This situation is unlikely to arise if the electrode has a resistance sufficiently low to avoid dangerous voltages to earth. However, onsite resistivity testing should always be carried out prior to carrying out an earth system design and installation. 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 lower than some types of soil. 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.
A waterlogged location is not essential unless the soil is sand or gravel. Care should be taken to avoid a site where water flows over it e. The resistance R should be taken as the ratio of the voltage between the inner electrodes and the current between the outer electrodes.
It is important that consideration is given to the possibility of corrosion of the metalwork reinforcement. It includes a number of editorial changes which clarify the meaning of the text and corrects values and symbols. 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.
Second important characteristic of earthing connection is that it MUST be capable bx carrying the maximum expected fault current. The faster, easier way to work with standards. Where the plate is placed in a cut out slot, e. Effective earthing safeguards people from the risk of electric shock. After construction and with the passage of time this moisture content will approach equilibrium with that of the soil, and will usually be dryer than when first laid. Foundation metalwork in concrete may be used as a ready made and effective earth electrode.
This applies particularly to surfaces which might have been primed before assembly. Where there is an option, a site should be chosen in one of the following types of situations in the order of preference given: Thus a pipe rod or strip has a much lower resistance than a plate of equal surface area. They may be used to give an indication of the difficulties that one might face in preparing an adequate design at the chosen location.
The products of corrosion occupy a greater volume than the original metal and cracking might occur. This may be taken as an indication of the possible gain from driving deeper rods, etc. Coke breeze should also not be used due to its highly corrosive nature. 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 sarthing. The effect of shape on an electrode resistance is related to the current density around the particular electrode considered.
This connection eartuing have a resistance not greater than that required to operate safety mechanisms to isolate the electricity supply from a fault situation. The minimum ground cover should not be less than mm and ideally the surrounding soil should be damp. Where the structure is supported on many similar footings, it may be considered feasible and more satisfactory to measure the resistance of one footing before it is electrically connected to othersand before there are any other electrically vs footings close by.
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. 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. The effect of other reinforcement which might be attached by wire ties only, may be neglected.
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.
If possible, it is advantageous and recommended to measure the resistance of several such footings to gain an indication of the likely variation of resistance. 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.
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.
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.
Corrosion of concrete encased steelwork, subject to a. This section deals only with a straight run of conductor. The finished joint should be covered with a heavy coat of bitumen.
Dry sand, gravel, chalk, limestone, whinstone, granite, any very stony ground, and all locations where virgin rock is very close to the surface should be avoided if possible.
It is of particular relevance to: It is important to ensure electrical continuity between all metalwork considered to be part of the electrode.
Measurements and Calculations Of Earth Electrode Systems (BS ) | EEP
The value of resistance required might not always be amenable to an automatically set value. Search all products by. This may be achieved by earthibg the dimensions in one direction large by comparison to the other two.
Accept and continue Learn more about the cookies we use and how to change your settings. Table 1 gives examples of resistivity only.