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.
|Published (Last):||12 February 2016|
|PDF File Size:||2.81 Mb|
|ePub File Size:||9.1 Mb|
|Price:||Free* [*Free Regsitration Required]|
There are commercially available materials to achieve this effectively, eadthing 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. It covers earthing system design parameters for structures, electrical equipment and systems.
Therefore any part of an electrode system which is less that 0. 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. 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 long after installation can vary gs7430 from the original test results.
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. Find Similar Items This product falls into the following categories.
Plates, if used, should be installed as small units of not greater than 1. Where the plate is placed in a cut out slot, e. The purpose of earthing System earthing involves the provision of a connection to the general mass of earth. It also includes some technical changes to correct and clarify formulae and equations. Premium Membership Premium membership gives you an access to specialized technical articles and extra premium content electrical guides and software.
The resistance to earth of a given electrode depends upon the electrical resistivity of the soil. 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.
Measurements and Calculations Of Earth Electrode Systems (BS ) | EEP
This is lower than some types of soil. The products of corrosion occupy a greater volume than the original metal and cracking might occur. 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.
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. Facebook Linkedin Google Plus Twitter. Effective earthing safeguards people fpr the risk of electric shock.
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. To obtain a low overall resistance the current density should be as low as possible in the medium surrounding the electrode. Measurements of the soil resistivity for the pre-determination of the resistance to prractice or the impedance to earth should be carried out using a four probe method widely known as the Wenner method as follows.
It is important to ensure that their resistance areas do not overlap. Worldwide Standards We can source any standard from anywhere in the world. This may be achieved by making the dimensions in one direction large by comparison to the other two.
Learn more about the cookies we use and how to change your settings. If possible, it is advantageous and recommended to measure the resistance of coe such footings to gain an indication of the likely variation of resistance.
Foundation metalwork in concrete may be used as a ready made and effective earth electrode. An earthing system should earthig 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. 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. Who is this standard for?
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.
The total electrode area formed by the underground ba7430 of large structure may often be used to provide an earth resistance lower then that obtainable by other methods. 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. The value of resistance required might not always be amenable to an automatically set value.
This applies particularly to surfaces which might have been primed before assembly.
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. System earthing involves the provision of a connection earthingg the general mass of earth.
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. Where there is an option, a site should be chosen in one of the following types of situations in the order of preference given: Coke breeze should also not be practife due to its highly corrosive nature.
It should be noted that these types of measurement are not rpactice 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 section deals only with a straight run of conductor.
Table 1 gives examples of resistivity only. 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. Melvin Surita Mar 07, 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.
The connecting strip to the above ground disconnection point should be fully insulated to avoid electrolytic action. 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.
Connections to the plate should be by copper conductor, welded, riveted or otherwise attached with codd that will not cause corrosion at the joint. Care should be taken to avoid a site where water flows over it e.
Alternating current should not be expected to cause corrosion, but, rectification sufficient to produce a very small proportion of direct current might take place.