Evaluating the Impacts of Grounding Systems on Ground Currents and Transient Overvoltage

This article presents a performance comparison of the solid, low impedance, high impedance, frequency-selective, and isolated grounding systems. A grounding system (for any power system component) is designed as an impedance ((Z) over bar (G)) that connects the neutral point to the ground. The impedance (Z) over bar (G) is constructed using a combination of R, L, and C elements. The values and combination type (series or parallel) ofR, L, and C determine the possible influence of (Z) over bar (G) on ground currents and potentials. Each grounding system is related to a system voltages level, a specific combination of R, L, and C, and a range of R, L, and C values. The solid, low impedance, high impedance, frequency-selective, and isolated grounding systems are designed for a 3 phi transformer and a 3f synchronous generator in order to compare their influences on ground currents and potentials during ground faults. The transformer and generator are tested for line-to-ground and double line-to-ground faults with all designed grounding systems. Test results show that some grounding systems can reduce ground currents only, while others can reduce ground potentials only. Such capabilities can be used to fulfill certain system and operation requirements (e.g., service continuity, ground capacity, etc.).