Optimal Design Of Substation Grounding Systems

Abstract

Substations being important linkage between various parts of entire power system, its role is crucial in overall functionality of the integrated power system. Substations in gen- eral can be considered as heart of entire power system because successful operation of any power system depends to a great extent upon pro cient and satisfactory performance of substations. In such substations, electrical safety is one of the most basic and important requirements. Responsibility of keeping the substation safe is upon the grounding sys- tem installed within it. In any substation deliberately planned earthing system plays an important role since absence of reliable and e ective grounding system can result in mal- operation or non-operation of control and protective devices and may prove hazardous for persons working therein. Also operation and safety of the equipments installed in the substation may be threatened. Therefore grounding system design is a task that deserves signi cant responsiveness because it deals with personnel safety and operation and pro- tection of the major equipments. This report is aimed at describing the development of and utilization of software for opti- mal design of substation grounding systems. IEEE standard 80 - 2000 is one of the widely accepted documents pertinent to safe practices to be followed while designing grounding systems for electrical substations. Here IEEE methodology for design of grounding system is implemented in computer programming environment. Software named ` Economical Substation Grounding System Designer (ESGSD) ' has been developed using MATLAB as mathematical computing tool as well as programming platform. ESGSD has been deployed as windows standalone application using MATLAB runtime compiler add on so that it can be used on the computer even where MATLAB is not installed. Working of ESGSD is divided in main two parts 1. It allows simple performance analysis for grounding system having ground grid of any of the ve basic shapes. It follows IEEE criteria for this purpose and additionally allows modeling of soil as two layered structure. 2. By selecting appropriate optimization options, ESGSD is able to give optimal design of substation grounding system for grounding grids having any of the basic shapes and located in uniform or two layered soil. In addition to grounding system analysis and optimization, ESGSD allows derivation of soil model from available Earth Resistance Testing (ERT) data. It can extract both type of soil models i.e. uniform and two layered soil models from available test data, to be used in further calculations. Performance of the software is evaluated by comparison with Ground Grid Systems (GGS) module of ETAP. Sample design problems solved with the help of both the software produce quite comparable results in majority of the cases. Thus by such software testing, technical soundness of the software is proved. In certain cases ESGSD is found to be superior than ETAP where the latter fails in applying optimization or gives unrealistic results that can not be practically implemented. By the end of the project, standalone application ESGSD is available which is able to analyze and optimize the design of the grounding system for any substation. This can be used appreciably as an educational tool for students of electrical engineering or train- ing tool for professionals concerned with substation designing. Also it gives satisfactorily accurate and optimal preliminary design of grounding system of any substation. Based on site speci c requirements and geometrical or any other constraints, detailed grounding system design can be prepared by the designer and again analyzed for the safety perfor- mance by this software. Also this work has exploited GUIDE facility of MATLAB for software development. Use of MATLAB runtime compiler has facilitated deployment of the software as standalone application to be used in absence of MATLAB. This is for the rst time that MATLAB is used for such extensive application development apart from its conventional use for simple coding and simulations. This draws attention towards yet another powerful feature of MATLAB for GUI development that can be helpful for those MATLAB users who like to develop applications but are not expert in professional software languages.