RCDs are designed for home and industrial applications. Their design is based on the classic principle of operation of a permanent magnet and a polarized relay. The advantage of such a solution is the independence of the protective functions from the voltage. The correct voltage value is only necessary during the periodic test of the RCD using the "T" button. RCDs should be tested regularly every month. The 6kA version of the Ex9L-N residual current circuit breakers is intended mainly for undemanding applications, such as basic protection in domestic installations.