Apparatuses and methods for passively monitoring the integrity of current sensing devices and associated circuitry in protective devices such as Ground Fault Circuit Interrupters and Arc Fault Circuit Interrupters are provided. A protection circuit interrupter employs a capacitively coupled noise signal obtained by an arrangement of one or both of the line side arms relative to a Rogowski coil. The noise signal is monitored while the line and load sides of a protective circuit interrupter are disconnected, and the connection of the line and load sides disabled if the noise signal fails to correlate sufficiently to a reference noise cycle. When the line and load sides are connected, the RMS value of the observed current signal is monitored such that the line and load sides are disconnected if the observed current signal fails to meet an RMS threshold. The observed current signal is otherwise compensated by subtracting the reference noise cycle prior to monitoring for the fault condition applicable to the protective device.

There is provided a method of operating a reconfigurable differential protection scheme for carrying out differential protection of an electrical power network, the electrical power network comprising terminals, each of the terminals configured to be in communication with each other within a communications network. The method includes controlling the differential protection scheme to deactivate the differential protection, and selecting a terminal to be configured out of or into the differential protection scheme. The method also includes communicating reconfiguration information among the terminals, the reconfiguration information including the selection of the terminal to be configured out of or into the differential protection scheme. The method also includes modifying a respective differential protection algorithm at each of the non-selected terminals so as to configure the selected terminal out of or into the differential protection scheme, and controlling the differential protection scheme to reactivate the differential protection.

There is provided a method of operating a reconfigurable differential protection scheme for carrying out differential protection of an electrical power network, the electrical power network comprising terminals, each of the terminals configured to be in communication with each other within a communications network. The method includes controlling the differential protection scheme to deactivate the differential protection, and selecting a terminal to be configured out of or into the differential protection scheme. The method also includes communicating reconfiguration information among the terminals, the reconfiguration information including the selection of the terminal to be configured out of or into the differential protection scheme. The method also includes modifying a respective differential protection algorithm at each of the non-selected terminals so as to configure the selected terminal out of or into the differential protection scheme, and controlling the differential protection scheme to reactivate the differential protection.

In differential protection schemes for electrical power systems there is a need to employ a synchronization technique to enable time alignment of local terminal current with received current from a remote terminal in order reliably to operate the differential protection scheme. A method of determining a communication time delay in a communication network between a local terminal and each of a plurality of remote terminals in a multi-terminal multi junction electrical power system includes: (a) calculating a respective initial communication time delay between each remote terminal and the local terminal; (b) calculating a respective junction time delay between respective first, second and third pairs of adjacent junctions; and (c) correcting the calculated initial communication time delay of each remote terminal spaced from the local terminal by two or more junctions according to each corresponding junction time delay arising between the or each said remote terminal and the local terminal.

In differential protection schemes for electrical power systems there is a need to employ a synchronization technique to enable time alignment of local terminal current with received current from a remote terminal in order reliably to operate the differential protection scheme. A method of determining a communication time delay in a communication network between a local terminal and each of a plurality of remote terminals in a multi-terminal multi junction electrical power system includes: (a) calculating a respective initial communication time delay between each remote terminal and the local terminal; (b) calculating a respective junction time delay between respective first, second and third pairs of adjacent junctions; and (c) correcting the calculated initial communication time delay of each remote terminal spaced from the local terminal by two or more junctions according to each corresponding junction time delay arising between the or each said remote terminal and the local terminal.

A power system includes: a self-commutated power converter including a first arm and a second arm, each including switching elements; a first circuit breaker configured to interrupt a current flowing through a power transmission line provided between a first bus and a second bus; a first circuit breaker control unit configured to control the first circuit breaker; a converter control unit configured to stop the switching elements based on a first arm current value and a second arm current value; and a setting unit configured to set a voltage value of an AC voltage output from the power converter such that when a fault occurs in the power transmission line, the first circuit breaker is opened while the switching elements are not stopped. The converter control unit is configured to operate the switching elements such that an AC voltage with the set voltage value is output.

A protection circuit for a capacitive filter for a multi-voltage system includes a first capacitor electrically connected between a first connection point at a first electrical potential and a second connection point at a second electrical potential and a second capacitor electrically connected between the second connection point and a third connection point at a third electrical potential. The first electrical potential is greater than the second electrical potential and the third electrical potential is less than the second electrical potential. The third electrical potential may be electrical ground. A controller circuit monitors a voltage differential across the first capacitor and the second capacitor and, based on the voltage differential meeting a threshold condition, controls a switch to disconnect one or both of the first capacitor and the second capacitor.

A protection circuit for a capacitive filter for a multi-voltage system includes a first capacitor electrically connected between a first connection point at a first electrical potential and a second connection point at a second electrical potential and a second capacitor electrically connected between the second connection point and a third connection point at a third electrical potential. The first electrical potential is greater than the second electrical potential and the third electrical potential is less than the second electrical potential. The third electrical potential may be electrical ground. A controller circuit monitors a voltage differential across the first capacitor and the second capacitor and, based on the voltage differential meeting a threshold condition, controls a switch to disconnect one or both of the first capacitor and the second capacitor.

The present disclosure relates to a method for preventing a maloperation of differential protection of an optical fiber caused by saturation of a single Current Transformer (CT) of 3/2 connection. By applying a combination of the differential judgment and the sub-CT current judgment, reliable identification of internal and external faults is ensured, and the problem of misjudging of the internal fault as the external fault can be prevented as well.

Apparatuses and methods for passively monitoring the integrity of current sensing devices and associated circuitry in protective devices such as Ground Fault Circuit Interrupters and Arc Fault Circuit Interrupters are provided. A protection circuit interrupter employs a capacitively coupled noise signal obtained by an arrangement of one or both of the line side arms relative to a Rogowski coil. The noise signal is monitored while the line and load sides of a protective circuit interrupter are disconnected, and the connection of the line and load sides disabled if the noise signal fails to correlate sufficiently to a reference noise cycle. When the line and load sides are connected, the RMS value of the observed current signal is monitored such that the line and load sides are disconnected if the observed current signal fails to meet an RMS threshold. The observed current signal is otherwise compensated by subtracting the reference noise cycle prior to monitoring for the fault condition applicable to the protective device.