Abb Schweiz Ag

Hitachi Energy Ltd

Abb Power Grids Switzerland Ag

Zhanpeng Shi

Ivo Brncic

Kai Liu

Jianping Wang

YouYi Li

Youyi Li

Sören Forsman

There is provided mechanisms for differential protection of a transmission line () of a transmission system (). A method comprises obtaining a restraining current and a differential current from the transmission line (S). The method comprises determining a compensation current for the differential current (S). The method comprises 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 (S). The method comprises detecting an internal fault for the transmission system (S). The method comprises, as a result thereof, 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 (S).

Differential protection of a transmission line

A method of current differential protection performed in a control device is disclosed, wherein the control device has a first operate-restrain characteristic with a differential characteristic pick-up setting I. The method includes: determining currents of all terminals of a protected object; determining a differential current based on the determined currents; determining direct current, DC, components in the respective determined currents; detecting a fault; and adjusting, for a detected external fault, the operate-restrain characteristics by setting an adjusted differential characteristic pick-up setting Ito be equal to the sum of the differential characteristic pick-up setting Iand the determined DC components, providing an adapted operate-restrain characteristics. Corresponding control device, computer program and computer program product are also disclosed.

Method and control device for current differential protection

The present invention discloses a method for detecting a fault and a current differential protection system thereof. The method for detecting fault includes calculating fault component currents, calculating an operate current and a restraint current of all terminals, and adjusting an operate level by adapting an operate-restraint characteristic according to a fault component. The method has very small operating area for external faults, which makes the method very reliable even for the case with serious CT saturation. A very big operating area for internal faults makes the method very sensitive for internal faults even for a heavy load and high resistance fault.

Method for detecting fault and current differential protection system thereof

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Västerås, Sweden

Zhanpeng Shi