Machines outages are costly and troubleshooting can be problematic. Often the reason can be that modern machines have modern loads built into them. Mains filters can cause disturbances to the incoming line and can change the behaviour of the RCD in series. More often, loads have single phase inverters built in. High frequency and extended DC immunity incorporated in a protection device, which is also high surge current proof, enables the next generation of machines to be safe above the levels stipulated by the standard.