As the level of automation in production and process systems increases, the number of loads powered by 24 volt direct current – controllers, sensors and electric motors – also continues to increase. The current in these circuits is usually provided by power supply units. Power supply units cut the power when a nominal value is exceeded and connected loads fail; therefore, circuit breakers protect individual components or groups of components in order to limit the effects of overcurrents and short circuits. However, conventional automatic thermal-magnetic circuit breakers require a high overcurrent to reliably trip. The necessary cut-off current may even be greater than the maximum current provided by the power supply. That makes fast, reliable shut-down in the event of short circuit impossible. In addition, capacitive loads, long cables or the simultaneous start-up of several 24 volt loads may cause additional challenges for the power supply and fusing.