Real-Time Monitoring of Substation Ground Potential Rise and Grounding System Impedance Using Power System Faults

Grounding system engineers and power utility owners have a duty of care to ensure that substation grounding systems continue to meet their safety performance requirements over the operational lifetime of the installation. Changes to power system or third-party assets associated with an installation, as well as environmental factors such as temperature or moisture level fluctuations, can cause variation in a grounding system´s performance. To perform a grounding system assessment, engineers must select a suitable set of fault scenarios on which to base their assessments. However, the relative risk level of hazards produced by a ground fault (GF) depends on that proportion of the fault current that passes to ground through the local grounding of the installation and the duration of the event. The consideration of all hazards posed by a single installation is thus physically and theoretically an expensive proposition, particularly for installations with complex grounding systems. An electronic recording system is proposed to capture the characteristics of power system ground potential rise (GPR) events during GFs. This system allows the failure of critical grounding system components to be highlighted as indicated by a substantial change in the measured impedance. The system also establishes the GPR event frequency, allowing the probabilistic nature of GFs associated with an installation to be assessed. This paper provides an explanation of the GPR monitoring rationale and a methodology for implementing such a system, and typical results are shown from trials undertaken in recent years.