Abstract: A method and a device provide protection for a multi-terminal HVDC grid against faults. The method includes measuring a DC displacement voltage having a polarity and a value, determining if a short circuit fault exists by comparing the DC displacement voltage with a threshold displacement voltage and identifying a fault type based on the polarity and the value of the DC displacement voltage. The disclosed device contains a converter having a positive pole and a negative pole, a DC-switch substation, a DC line connecting the converter and the DC-switch substation and a transient fault detector. The transient fault detector contains a positive voltage sensor sensing a positive transient voltage of the positive pole and a negative voltage sensor sensing a negative transient voltage of the negative pole and a control unit which is adapted to derive a DC displacement voltage from the positive and the negative transient voltages.

Abstract: A method protects an electrical generator or power station unit connected to a power distribution network or to a power transmission line. A short circuit near the generator in the power distribution network or on the power transmission line is detected, and a short-circuit detection signal is generated, when a set of predetermined trigger conditions is satisfied. The electrical generator is disconnected from the network or line if, after generation of the short-circuit detection signal, the trigger conditions are satisfied at the instant when a predetermined delay time elapses, and have remained satisfied until the predetermined delay time elapses. The delay time is a variable duration which is reestablished regularly or irregularly before it elapses, as a function of the operating profile after the short-circuit occurrence, and the generator is disconnected if the trigger conditions are satisfied at the instant when the delay time elapses.

Abstract: A method protects an electrical generator or power station unit connected to a power distribution network or to a power transmission line. A short circuit near the generator in the power distribution network or on the power transmission line is detected, and a short-circuit detection signal is generated, when a set of predetermined trigger conditions is satisfied. The electrical generator is disconnected from the network or line if, after generation of the short-circuit detection signal, the trigger conditions are satisfied at the instant when a predetermined delay time elapses, and have remained satisfied until the predetermined delay time elapses. The delay time is a variable duration which is reestablished regularly or irregularly before it elapses, as a function of the operating profile after the short-circuit occurrence, and the generator is disconnected if the trigger conditions are satisfied at the instant when the delay time elapses.

Abstract: A method and a device provide protection for a multi-terminal HVDC grid against faults. The method includes measuring a DC displacement voltage having a polarity and a value, determining if a short circuit fault exists by comparing the DC displacement voltage with a threshold displacement voltage and identifying a fault type based on the polarity and the value of the DC displacement voltage. The disclosed device contains a converter having a positive pole and a negative pole, a DC-switch substation, a DC line connecting the converter and the DC-switch substation and a transient fault detector. The transient fault detector contains a positive voltage sensor sensing a positive transient voltage of the positive pole and a negative voltage sensor sensing a negative transient voltage of the negative pole and a control unit which is adapted to derive a DC displacement voltage from the positive and the negative transient voltages.