Grounding Method for Reliable Operation of Power and Distribution Transformers Substations

Equipment grounding is a necessary and conclusive parts of an installation process in electrical power
system networks particularly in power substations. Over years, grounding or earthing of substations
has been carried out primarily through preparation of an earth mat which is simply interconnected with
several Earth-rods buried around the substation or any other equipment under installation. Apart from
the fact that this approach is old, it is in addition required several efforts to have an acceptable and
reliable results. Thus, a more sophisticated, reliable and results oriented is required to be in place.
This paper presents a modern approach to earthing of transformer substations and other allied
equipment. The approach negates the constraints that are obtained in the old approach. A 15MVA,
33/11kV power transformer substation as well as a 500kVA, 11/0.415kV distribution transformer
substation’s installations were selected as the case study. A flow chart which describe the procedures
of carrying out the proposed modern method of earthing is developed and applied to the two case
studies. The various earth resistances measured on both cases are presented and discussed. The
results from these case study indicates that the earth resistance values obtained from this new
approach are reliable and in compliance with IEEE Standards 80,142, 81 and 1100.