In view of the problem of destructive discharge of pole-mounted circuit breaker due to excessive potential of enclosure to ground during the power frequency voltage test of the load side or power side of the existing primary and secondary fusion pole-mounted circuit breaker with EVT (electronic voltage transformer)

the insulation performance across-open contacts of the pole-mounted circuit breaker with EVT configuration is studied int his paper. Firstly

capacitance distribution theoretical analysis of the enclosure to ground discharge problem during the withstanding voltage test across open contacts of the pole-mounted circuit breaker is performed

and the voltage between the enclosure and ground during the withstanding voltage test across open contacts of pole-mounted circuit breaker made of EVT with different capacitance values is given. Secondly

the theoretical design basis for the existing China national grid standardization scheme on the primary and secondary fusion pole-mounted circuit breaker is given and the insulation design margin of the primary and secondary fusion pole-mounted circuit breaker equipped with EVT on the power side is pointed out. It is concluded that under the premise of meeting the requirements of switching performance and EVT accuracy

the capacitor with low capacitance value is used as much as possible for the HV arm of EVT so to reduce the the voltage of enclosure to the ground. Finally

a new structure of the primary and secondary fusion pole-mounted circuit breaker with EVT on both the load side and the power side is proposed under the existing test method

and the test results are given. The analysis and test results prove that in case of withstanding voltage test across the open contacts of the pole -mounted circuit breaker with the structure

the voltage of the enclosure to ground is less than 42 kV (phase to ground voltage) specified by GB/T 11022—2020

which avoids the phenomenon of the enclosure to ground breakdown during the withstanding voltage test across open contacts and the results have been widely used in engineering.