Differential Protection of a Transmission Line

A method for differential protection of a transmission line of a transmission system, the method comprising:

• obtaining a restraining current and a differential current from the transmission line;
• determining a compensation current for the differential current;
• providing the differential current as compensated for by the compensation current and the restraining current to a differential protection arrangement for making a trip decision;
• detecting an internal fault for the transmission system;
• and
• in response to detecting the internal fault, providing the differential current without being compensated for by the compensation current and the restraining current to the differential protection arrangement for making the trip decision.

An arrangement for differential protection of a transmission line of a transmission system, the arrangement comprising processing circuitry, the processing circuitry being configured to cause the arrangement to:

• obtain a restraining current and a differential current from the transmission line;
• determine a compensation current for the differential current;
• provide the differential current as compensated for by the compensation current and the restraining current to a differential protection arrangement for making a trip decision;
• detect an internal fault for the transmission system;
• and
• in response to detecting the internal fault, provide the differential current without being compensated for by the compensation current and the restraining current to the differential protection arrangement for making the trip decision.

A computer program for differential protection of a transmission line of a transmission system, the computer program comprising computer code which, when run on processing circuitry of an arrangement, causes the arrangement to:

• obtain a restraining current and a differential current from the transmission line;
• determine a compensation current for the differential current;
• provide the differential current as compensated for by the compensation current and the restraining current to a differential protection arrangement for making a trip decision;
• detect an internal fault for the transmission system;
• and
• in response to detecting the internal fault, provide the differential current without being compensated for by the compensation current and the restraining current to the differential protection arrangement for making the trip decision.