Electric power supply network, especially for a vehicle, and short-circuit detection process in this network

The system has a first conductor system (1) for a higher voltage and a second (2) for a lower voltage. The conductor systems have a first or second protection element (9,10) and contain an electrical load (3,4) and a common voltage reference point. A voltage comparator (14) is provided that taps the voltage on the input and output (15,16) of the second protection element (10) to detect a short circuit between the conductor systems. Independent claims are also included for the following: a method of detecting a short circuit in a supply system.