The grounding system of a high voltage substation is responsible for moderating the step and touch voltages inside the yard and outside the fence. This ensures the safety of personnel working at the station and the nearby general public. The ground potential rise (GPR) in the event of fault must also be limited by installing an adequate low impedance grounding system. Recent advances in computer modelling and ground grid testing capabilities have raised questions regarding the performance of older grounding systems with respect to both design and integrity. Therefore, many utilities are interested in evaluating these systems using advanced testing and modelling solutions inorder to mitigate the identified deficiencies. This report begins with a comprehensive utility survey on the best practices in rehabilitating deficient grounding grid performance. This includes 55 questions in seven main categories and a summary of the received responses from 14 utilities. The next chapter presents the deficiencies seen at 100 transformer or switching stations reviewed and tested by Kinectrics over the past 15 years using a health index system. The third chapter reviews a number of mitigation solutions in moderating the step and touch voltages as well as the GPR using the advanced grounding software (CDEGS) in four different types of soil conditions. This section provides a general perspective on the effect of gradient control conductors, ground wells, and counterpoise conductors on improving the ground grid performance. Chapter 5 and 6 present the detailed conclusions and recommendations that are concluded from this work.
Substation Grounding, Step and Touch Voltage, GPR, Rehabilitation, Ground Grid Health Index, Electrical Safety