ASJ series residual current protection relay can be assembled with low voltage circuit breaker or low voltage contactor to form a combined residual current action protector. It is mainly suitable for distribution lines of TT and TN systems with AC 50Hz and rated voltage up to 400V. It is used for ground fault protection of electrical circuits to prevent equipment and electrical fire accidents caused by ground fault current, and can also be used to provide indirect contact protection for personal electric shock hazards.