Monitoring protection circuit for lighting installations

The invention relates to a monitoring protection circuit for lighting systems, which comprises a lighting unit, a power supply, and a measuring device measuring electrical quantities, as well as a method which uses the monitoring protection circuit. The object of providing a monitoring protection circuit which is suitable for detecting fault resistances in the lighting system is solved in that a monitoring protection circuit, which comprises a load switch switching the lighting unit on and off and a current and/or voltage limiting component, is used such that upon coincidence of the measured voltage U L across the lighting unit with the expected voltage U Soll or of the measured current I L through the measurement path with the expected current I Soll from the target current-voltage characteristic curve of the lighting unit, the lighting unit is switched on, and upon a definable deviation of the voltage U L across the lighting unit from the expected voltage U Soll or of the current I L from the expected current I Soll from the target current-voltage characteristic curve of the lighting unit, the lighting unit is switched off immediately.