Generally, provision of effective earthing system depends on aim and goal involved, and the environment where the earthing or grounding as the case may be, is actually required. For instance in Power Engineering, providing adequate Earthing in a substation is an important essential safety measure. The aim and goal is to provide under and around the substation, a surface of uniform potential, at near or absolute zero earth potential.
In some cases, earthing or Grounding terminology is commonly used to mean the same thing. However, the two technical terminologies have distinction. Earthing is the connection of non-current carrying parts to ground. Example: All metallic enclosure. This is for Human safety. While, Grounding is the connection of current carrying parts to the ground. Example: Generator or Transformer Neutral. This is for Equipment safety.
Substation Earthing is also crucial and essential for effectiveness of protection and control devices, apparatus and equipment, in its efficient operations and performances. Consequently, a proper and appropriate "Earthing System Grid Design and Design Calculation" have to be embarked upon, grid mesh has to be formed, The Conductor Length Required for Gradient Control has to be determined, Numbers of Grounding Rods have to be determined, Fault MVA has to be Calculated, Soil resistivity has to be measured, Grounding Fault Current has to be Calculated etc; All the needed parameters and data are to be got through the various equations and applied properly, because there is no room for speculation, gambling or/and trial and error approach. Through the Power System Grid Design and its Design Calculation, the application of the outcome result and various values got from the various formula and Guidelines provided by IEEE std 80 (2000) R<<1 ohm will be obtain, and (Ground Potential Rise), GPR < Etouch, Em < Etouch and Es < Estep will be achieved. All these will guarantee Human and Equipment Safety.
Advance Technology and series of Researches carried out using sophisticated measuring Instruments and standard Constant Values derived from these extensive researches, such as for the following parameters: Ambient Temperature, Maximum Allowable Temperature Fault Duration Time, Temperature of Thermal Coefficient of Resistivity at Zero Degree Centigrade, Thermal Coefficient of Resistivity at reference temperature, Thermal Capacity Factor, Depth of Burial Grid, Reference Depth Grid, Surface Layer Resistivity, Diameter of Grid Conductor, etc, couple with various derived Standard Equations used in Earthing System Grid Design and Design Calculation to get length of appropriate copper conductor and other required necessary parameter and quantity of electrodes plus addition of a mixture of Charcoal, Saline and Soil has overtaking the use of smelling animal dung, as used in the 50s.
The design method is very accurate as to the eventual result after the execution of all recommended procedure and materials for its application in either Distribution or Transmission Substations where 15MVA, 30MVA, 45MVA, 60MVA to 150MVA Power Transformers at Voltage Levels of 33/11KV, 132/33KV and 330/132KV with their Associated Equipment are concerned. However, if the aim and goal is just to provide earthing for smaller and one or two Equipment, then standard earth mat, one or two copper electrodes, charcoal and saline will be okay for improving the earthing.
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