UHV live tank circuit breaker is made of interrupter with multi-breaks. The open contacts of the circuit breaker is with grading capacitor in parallel since due to the uneven voltage distribution of each break by the distributed capacitance when the breaker is in operation in the grid in order to assure even voltage distribution of each break. In this paper

the 1 100 kV live tank circuit breaker is taken as the study object

the distributed capacitance across open contacts of the circuit breaker is calculated by the definite element analysis software of the ANSYS

the equivalent capacitance model is set up by the digital simulation software ATP to calculate uneven coefficient of voltage for each open contacts at different capacitor allocation mode. It is shown by the calculation result that when the capacitance of shunt capacitors in the four open contacts of the live tank circuit breaker is 2 500 pF

2 000 pF

2 000 pF and 2 500 pF respectively

the voltage uneven coefficient for each open contacts is less than 1.1 and the voltage distribution is fairly even.