ABSTRACT
Safety, system protection and performance are the three main reasons of effectively earthing a power system and electrical equipments. Earthing practices errors due to lack of understanding of the subject and harsh tropical soil environmental factors have caused unexplained death and fire outbreaks. Thus the objective of this work is to investigate factors responsible for poor earthing systems performance in tropical environments.
The methodology employed in this study starts with the measurements of the dc earth electrode resistances of some existing earthing systems in tropical environments with Nigeria as a study case, to ascertain the level of compliance with the National codes on earthing. This was followed by an in-depth survey of soil resistivities with the focus on the influence of environmental factors on resistivity values variations and the laboratory measurements of biological wastes collected from poultry farms, cattle markets, saw mills and specialized latrines to ascertain their suitability as soil enhancing materials.
Earthing system models were developed from both the analytical and the numerical approaches and parametric analysis were carried out with the developed models to illustrate the parameters with dominant influence on the earth electrode resistance of an earthing configuration. The analysis reveals some possibilities of optimally configuring the earth electrodes to achieve an efficient and effective earthing system.
The investigations show that lack of preliminary design procedures, high soil resistivities as a result of environmental temperatures and soil topography, the use of low quality materials and lack of periodic inspection and maintenance culture are some of the notable factors responsible for the poor earthing system performance in tropical environments
The results of the laboratory analysis where biological wastes were investigated for their soil enhancing properties show that they can be used as soil enhancing material as they possess low resistivities at 50% by weight of water. They also possess high moisture retention qualities with wood ash, organic manure, chicken wastes in that order showing good performances. The study on their electrolytic content durability for the past three years shows that they still maintain low earth electrode resistance qualities with embedded earth electrodes due to their high electrolytic content chracteristics.
