Patent ID: 8842401

Claim:
A protection system for a DC electrical power network, the system having: at least one convertor for connection of a power supply or load to the network, the convertor having an output capacitor; one or more circuit breaker arrangements which on activation isolate electrical faults within the network; one or more fault detectors including a sensor for measuring the voltage drop, V CF , across the output capacitor and the rate of change of current, di/dt, at the output capacitor; and a fault type identification arrangement which receives from the fault detectors the measured rates of change of current, di/dt, determines therefrom second derivatives of current, d2i/dt2, across the capacitances, and identifies fault types from the second derivatives, wherein the or each fault detector measures an inductance of a respective section of the network, the system being configured to activate one or more of the circuit breaker arrangements in response to measured inductances which are indicative of a fault, and the inductance of the respective section is determined from V CF /(di/dt).