Fault detection of a transmission line

An arrangement for detecting a fault of a transmission line in a power system comprising at least one of an extreme weak system and an extreme strong system, the arrangement comprising a processing unit, the processing unit being configured to cause the arrangement to:

• obtain travelling wave polarities from two terminals of the transmission line during occurrence of the fault, the travelling wave polarities being defined by two current polarities (Δi1, Δi2) and two voltage polarities (Δu1, Δu2);
• determine some of the obtained travelling wave polarities to be detectable and some of the obtained travelling wave polarities to be non-detectable;
• and
• detect the fault to be internal based on the detectable travelling wave polarities and the non-detectable travelling wave polarities.

An arrangements for detecting a fault of a transmission line in a power system comprising at least one of an extreme weak system and an extreme strong system, the arrangement comprising:

• a communications module configured to obtain travelling wave polarities from two terminals of the transmission line during occurrence of the fault, the travelling wave polarities being defined by two current polarities (Δi1, Δi2) and two voltage polarities (Δu1, Δu2);
• a polarity detection module configured to determine some of the obtained travelling wave polarities to be detectable and some of the obtained travelling wave polarities to be non-detectable;
• and
• a fault detection module configured to detect the fault to be internal based on the detectable travelling wave polarities and the non-detectable travelling wave polarities.