Abstract: Loop resistance testing is a mandatory procedure for identifying poor contact defects in the generator electrical brake switch/generator circuit breaker(GEBS/GCB). However, there are currently no mature domestic or international devices capable of accurately measuring the conductive loop resistance of GEBS/GCB without disconnecting the grounding wires. To address this challenge, this study proposes a loop resistance detection technology based on large-diameter non-contact DC current measurement, supported by GEBS/GCB grounding network analysis, coupled network modeling and simulation, and advanced testing algorithms. Furthermore, a testing instrument has been developed based on the minimum network principle for loop resistance measurement. This innovation enables efficient, non-destructive, and safe GEBS/GCB loop resistance testing without disassembling the grounding busbars, thereby significantly improving testing efficiency and operational safety.