Verification of the dielectric withstand between the live part and the enclosure during the transformer capacitive synthetic tests for dead-tank breaker

In case of EHV (Extra High Voltage) and UHV (Ultra High Voltage) circuit breaker, almost all of testing laboratories adopt the single-phase testing method for verifying the performance of capacitive breaking capability, based on sub-clause 6.111 of IEC 62271-100, due to the limitation of testing facilities. For dead-tank breaker with 1.4 capacitive voltage factor, the tests for the dielectric withstand between the live part and the enclosure is recommended as a non-mandatory testing item. However, IEC MT36 has proposed the change of standard to specify as a mandatory in its next version planned in 2016. The peak recovery voltages between the live part and the enclosure, occurring just after interrupting capacitive currents, arrive at different values on supply and load sides. With the technical background, the new transformer capacitive current breaking test circuits are proposed to fulfill the next edition of IEC 62271-100 to be newly published in 2016. This paper illustrates the testing methods and simulation results for the transformer capacitive synthetic tests of single phase capacitive current breaking.