Calculation method for voltage distribution of the controlled metal oxide arrester

Equivalent capacitance of thyristor used in thyristor valve of the controlled metal oxide arrester (CMOA, shortly), C_T, changes with thyristor terminal voltage, φ_T. When voltage distribution of CMOA is calculated, such characteristic should be considered. Combining field-circuit combination method and variable rule of CT with φ_T, a calculation program was put forward. Firstly, electric field numerical calculation models of MOA1, MOA2 and MOR were made and an equivalent capacitance network was calculated. Then function of C_T and φ_T was solved by test and curve fitting. Secondly, equivalent circuit of CMOA was founded. The function of C_T and φ_T was substituted to the circuit. Function between electrode voltage, φ_Fi, and CMOA voltage, φ_s could be calculated by iterations. Finally, the function between φ_Fi and φ_s was substituted to electric field numerical calculation model and variable rule of voltage distribution by φ_s was solved. The calculation program was verified by tests. Results indicated that it was effective to calculate voltage distribution of CMOA.