Systems and methods to disconnect a faulted region of a power grid are described. For example, a control system may obtain a set of regions of a power grid. The control system may obtain a current magnitude and a voltage magnitude of the power grid. The control system may detect a fault in the power grid based at least in part on the current magnitude. The control system may, from the set of regions, determine a faulted region that the fault is located within based on a voltage magnitude of one or more buses in the power grid, a net change in power with respect to time of one or more regions in the set of regions, or both. The control system may send one or more signals to electrically disconnect the faulted region from the power grid.

An arrangement and method for zero sequence differential protection of a transmission line of a power system are disclosed. A zero sequence differential protection unit is configured to detect an internal fault of the transmission line using current measurements of each phase A, B, C of the transmission line. The zero sequence differential protection unit is configured to initiate a trip when an internal fault is detected. A phase selection unit is configured to determine whether or not any of the phases A, B, C of the transmission line is faulty using a comparison of differential values of the current measurements for each phase. The phase selection unit is configured to, based on the initiation of the trip, determine which of the phases A, B, C is faulty and to finalize the trip for any faulty phase.

Disclosed are a direct-current transmission line protection method and system based on pure current characteristics. The direct-current transmission line protection method based on pure current characteristics comprises: collecting, at a moment k.sub.0, a line current i.sub.M(k.sub.0) of an M side of a first direct-current transmission line and collecting, at a moment k.sub.0−t.sub.s, a line current i.sub.M(k.sub.0−t.sub.s) thereof, calculating, according to the line current i.sub.M(k.sub.0) and the line current i.sub.M(k.sub.0−t.sub.s), at a moment k.sub.0, a differential value di.sub.M(k.sub.0) of a current of the side of the first direct-current transmission line, and determining whether the differential value di.sub.M(k.sub.0) of the current meets a protection enabling criteria; and insofar as, at the moment k.sub.0, the differential value di.sub.M(k.sub.0) of the current of the M side of the first direct-current transmission line meets the protection enabling criterion, enabling direct-current protection for the M side of the first direct-current transmission line, collecting a line current i.sub.M(j) of the M side of the first direct-current transmission line at a moment j and collecting, at a moment j−t.sub.s, a line current i.sub.M(j−t.sub.s) thereof, and calculating, according to the line current i.sub.M(j) and the line current i.sub.M(j−t.sub.s), a differential value di.sub.M(j) of the current of the M side of the first direct-current transmission line at the moment j.

Systems and methods to disconnect a faulted region of a power grid are described. For example, a control system may obtain a set of regions of a power grid. The control system may obtain a current magnitude and a voltage magnitude of the power grid. The control system may detect a fault in the power grid based at least in part on the current magnitude. The control system may, from the set of regions, determine a faulted region that the fault is located within based on a voltage magnitude of one or more buses in the power grid, a net change in power with respect to time of one or more regions in the set of regions, or both. The control system may send one or more signals to electrically disconnect the faulted region from the power grid.

There is provided mechanisms for zero sequence differential protection of a transmission line of a power system. An arrangement comprises a zero sequence differential protection unit configured for, using current measurements of each phase A, B, C of the transmission line, internal fault detection of the transmission line. The arrangement comprises a phase selection unit configured for, using a comparison of differential values of the current measures for each phase, determination of whether any of the phases A, B, C of the transmission line is faulty or not. A trip is caused by the zero sequence differential protection unit when an internal fault is detected by the zero sequence differential protection unit, and the trip starts all the phases A, B, C for the phase selection unit to finalize the trip for said any faulty phase.