While being tested in direct test circuit

the tested circuit-breaker may be distroyed due to excessive long arcing time if it fails to clrar. It would get the designers of circuit-breakers into trouble. This paper introduces two special test circuirs with additional auxiliary interrupting device equipped with parallel capacitors and resistors. with these circuits the undue long arcing time and thus the explosion of tested circuitbreaker may be avoided. one of the test circuits can also provide a new approach to measure post-arc current.