A Multiple-Fault Diagnosis Method for Non-Uniform Grounding Grids Based on Dynamic Topology Tearing

Corrosion and conductor breaks in grounding grids can compromise the safe dissipation of substation fault currents. To diagnose these faults using only a limited number of accessible nodes, this study groups frequencies and selects reference-port impedances based on the distribution of injected currents throughout the grounding grid at different frequencies. The topology-tearing method retains all nodal voltages and employs equivalent sources to approximate the effects of currents in fixed branches. For a grounding grid comprising 49 branches, this method reduces the number of unknowns from 79 at low frequencies to 47 at high frequencies. The proposed hybrid algorithm (ERS-DBO-SQP) augments dung beetle optimization with reflection and scattering moves during stagnation and uses sequential quadratic programming for local refinement. In the selected timed run on this grid, ERS-DBO-SQP achieved a geometric mean of sensitivity and specificity of 0.8563 in 91.25 s of solver time. Three alternative solvers achieved 0.3801–0.4282 in 120.74–129.47 s. Numerical simulations, CDEGS simulations, and field tests demonstrate that the proposed method can effectively identify corrosion and conductor-break faults with high diagnostic accuracy.