Loop resistance measurement is an important part of the maintenance work for the high voltage circuit breaker. In this paper

an abnormal increase of loop resistance for porcelain post circuit breaker has been analyzed.Through the disassembly inspection of the circuit breaker

it has been found that the contact parts of the moving and fixed contacts of the arc extinguishing chamber are normal

and there is water accumulation and corrosion on the conductive contact surface between the terminal block and the flange. According to the flange structure

the equivalent circuit model is established

and the influence of flange water accumulation between conductive contact surfaces

corrosion on the loop resistance of the circuit breaker has been computed and analyzed. It is found that the flange water accumulation is one reason for the abnormal increase of loop resistance. The measurement results of loop resistance can be well explained by the equivalent circuit model. The research in this paper can provide computation and analysis support for this kind of loop resistance abnormal increase problem.