Study of different types of earthing in electrical installations

Abstract

Earthing of electrical installations is a complicated task upto some extent. It requires to follow necessary guide lines to achieve the most correct results. But in Sri Lanka, we don't have particular standards to follow when earthing circuit is designed. According to the assets to be protective from the required earthing circuit, it is designed and implemented. Large assets like power plants, substations and large factories etc. are protected by a well designed earthing network. Most probably this design includes, a reputed contractor who is using necessary software makes calculations etc. and a design is submitted. This submission is then reviewed by a consultant. When the implementation stage it is well .supervised and :finally it is tested at the commissioning of the said asset. When it comes to the domestic earthing, the engineer or technician uses his own experience to make the electrical system earthed. At this level most probably no calculations are done, no commissioning tests are done but the system is earthed to achieve a some earth resistance. This achievement is somewhat acceptable when the assets to be protected is considered. But when we take medium scale assets like distribution substations, auto re-closures etc., there are no common accepted standards for designing and implementation of earthing systems. Even in the Ceylon Electricity Board and LECO, there is no proper set of guide lines to be followed when it is going to design and implementation an earthing circuit for the same. Therefore the technology being used for implementation of earthing circuit is not related with the assets to be protective when these medium scale assets are considered. The purpose of this project is to develop a protocol which can be acceptable in making these earthing of medium scale assets