An HVDC Light transmission behaves differently compared to an AC or an HVDC Classic transmission if there is a ground fault or short circuit.
DC cable faults
Cable faults are very rare. They are as a rule caused by mechanical damage. Therefore submarine DC cables are often buried (except in deep waters) to prevent damage from anchors and trawls. When a DC cable fault occurs, this is detected, the converters are blocked and the transmission is disconnected from the AC grid at both ends.
AC network faults
When a temporary fault occurs in the AC system (on the rectifier or the inverter side), the HVDC Light transmission may suffer a power loss depending on the fault impedance and severity. As soon as the fault is cleared, power is restored to the pre-fault value.
At a permanent AC fault the converter will be blocked and disconnected from its AC grid. The other converter will stay connected and can continue to stabilize the AC voltage using the inherent reactive power capability.
Converter station faults
Most of the HVDC Light converter station equipment is located inside a building - a fact that provides the station with a good protection against flashovers.
HVDC Light converter stations are provided with an elaborate protection system that is designed to detect fault conditions or other abnormal conditions that might expose equipment to hazard and/or cause unacceptable disturbances. The converter will be blocked and disconnected from its AC grid. The other converter will stay connected and can continue to stabilize the AC voltage using the inherent reactive power capability.