Test Method for Transient Characteristics of Grounding Grid With Current Return Point Located in the Same Grid

Lightning strikes in substations may result in extremely uneven ground potential distribution, which will threaten the safety and stability of equipment in substation. However, the main parameters for evaluating the performance of grounding grids are grounding resistance and impulse impedance, and little attention is paid to the distribution of the transient ground potential differences. In addition, when measuring the impulse impedance of a grounding grid, the length of the current leads should be very large, which requires a high-capacity impulse generator to suppress the influence of lead inductance on current waveform. In this paper, a test method is proposed for the transient characteristics of grounding grid with the current-return point located in the same grid. The feasibility of the method is illustrated by analyzing the ground impedance between the current injection point and the return point, longitudinal current of the grounding conductor, transient ground potential rise and transient ground potential difference. The effects of parameters such as soil resistivity, lightning waveform, size of the grounding grid, spacing and materials of the grid conductor are discussed to demonstrate that the method can be applied to most substations. Finally, the practicality of the method is verified by experiments in a 220 kVsubstation.