Single phase broken conductor detection
The present disclosure relates to systems and methods to detect a fault in an electric power system. One embodiment may detect a single phase broken conductor in a multi-phase electric power system. An intelligent electronic device (IED) may receive a plurality of measurements over time of a current through an electrical conductor in the electric power system. Based on the measurements of the current, a fault detection subsystem may determine a zero-sequence current, a negative-sequence current, and a positive-sequence current. The fault detection subsystem may determine a ratio of the zero-sequence current, the negative-sequence current, and the positive-sequence current, and may monitor the ratio over time. The fault detection subsystem may identify the broken conductor condition based on the ratio and a fault detection region. A protective action subsystem may implement a protective action based on identification of the broken conductor condition.
1 . A system to detect a fault in an electric power system, the system comprising:
an intelligent electronic device (IED) to receive a plurality of measurements over time of a current through an electrical conductor in the electric power system;
a fault detection subsystem to monitor for a broken conductor condition and configured to:
determine a zero-sequence current based on the measurements of the current;
determine a negative-sequence current based on the measurements of the current;
determine a positive-sequence current based on the measurements of the current;
determine a ratio of the zero-sequence current, the negative-sequence current, and the positive-sequence current;
monitor the ratio over a time; and
identify the broken conductor condition based on the ratio; and
a protective action subsystem to implement a protective action based on identification of the broken conductor condition.
2 . The system of claim 1 , wherein the fault detection subsystem is further configured to:
determine a real component and an imaginary component of the ratio; and
identify the broken conductor condition when:
the real component of the ratio falls between a minimum ratio threshold and a maximum ratio threshold; and
the imaginary component of the ratio falls between a maximum angle threshold and a minimum angle threshold.
3 . The system of claim 2 , wherein the minimum ratio threshold and the maximum ratio threshold are defined between one of a fixed minimum real value and a fixed maximum real value, and a minimum radius and a maximum radius.
4 . The system of claim 1 , wherein the ratio comprises a sum of the zero-sequence current and the negative-sequence current, divided by the positive-sequence current.
5 . The system of claim 1 , wherein the plurality of measurements comprise only measurements from a local node.
6 . The system of claim 1 , wherein the electrical conductor comprises a suspended conductor and the protective action subsystem is configured to implement the protective action within a window defined by a time for the suspended conductor to fall to the ground.
7 . The system of claim 1 , wherein the electric power system comprises multiple phases, and the fault detection subsystem is further configured to monitor each phase.
8 . The system of claim 7 , wherein the fault detection subsystem is further configured to:
identify a phase with a minimum current; and
confirm that the phase with the minimum current corresponds to a phase associated with the broken conductor condition prior to implementation of the protective action.
9 . The system of claim 1 , wherein the fault detection subsystem is further configured to compare the positive-sequence current to a minimum current requirement, and to implement the protective action only when the positive-sequence current exceeds the minimum current requirement.
10 . The system of claim 1 , wherein the fault detection subsystem is further configured to identify at least one of a single-phase-ground fault, a phase-phase fault, a phase-phase-ground fault, and a 3-phase fault based on the ratio, and the protective action subsystem is further configured to implement the protective action based on identification of such a fault.
11 . The system of claim 1 , wherein the fault detection subsystem is further configured to:
identify a minimum phase current;
determine a magnitude of a phasor corresponding to the minimum phase current
determine an angle of the phasor corresponding to an angle of positive sequence voltage advanced by 90 degrees;
determine a refined ratio by subtracting the phasor from the ratio.
12 . The system of claim 11 , wherein the refined ratio compensates for the charging current of the electrical conductor.
13 . A method of detecting a fault in an electric power system, the method comprising:
receiving, using an intelligent electronic device (IED) a plurality of measurements over time of a current through an electrical conductor in the electric power system to monitor for a broken conductor condition;
determining, using a fault detection subsystem, a zero-sequence current based on a measurement of the current;
determining, using the fault detection subsystem, a negative-sequence current based on the measurement of the current;
determining, using the fault detection subsystem, a positive-sequence current based on the measurement of the current;
determining, using the fault detection subsystem, a ratio of the zero-sequence current, the negative-sequence current, and the positive-sequence current;
monitoring, using the fault detection subsystem, the ratio over a time;
identifying, using the fault detection subsystem, the broken conductor condition based on the ratio; and
implementing, using a protective action subsystem, a protective action based on identification of the broken conductor condition.
14 . The method of claim 13 , further comprising:
determining, using the fault detection subsystem, a real component and an imaginary component of the ratio;
identifying, using the fault detection subsystem, the broken conductor condition when:
the real component of the ratio falls between a minimum ratio threshold and a maximum ratio threshold; and
the imaginary component of the ratio falls between a maximum angle threshold and a minimum angle threshold.
15 . The method of claim 14 , wherein the minimum ratio threshold and the maximum ratio threshold are defined between one of a fixed minimum real value and a fixed maximum real value, and a minimum radius from an origin and a maximum radius from an origin.
16 . The method of claim 13 , wherein the ratio comprises a sum of the zero-sequence current and the negative-sequence current, divided by the positive-sequence current.
17 . The method of claim 13 , wherein the plurality of measurements comprise only measurements from a local node.
18 . The method of claim 13 , wherein the electrical conductor comprises a suspended conductor and the protective action subsystem is configured to implement the protective action within a window defined by the time for the suspended conductor to fall to the ground.
19 . The method of claim 13 , further comprising:
monitoring, using the fault detection subsystem, a plurality of phases.
20 . The method of claim 19 , further comprising:
identifying, using the fault detection subsystem, a phase with a minimum current; and
confirming, using the fault detection subsystem, that the phase with the minimum current corresponds to a phase associated with the broken conductor condition prior to implementing the protective action.
21 . The method of claim 13 , further comprising:
comparing, using the fault detection subsystem, the positive-sequence current to a minimum current requirement; and
implementing the protective action only when the positive-sequence current exceeds the minimum current requirement.
22 . The method of claim 13 , further comprising:
identifying, using the fault detection subsystem, at least one of a single-phase-ground fault, a phase-phase fault, a phase-phase-ground fault, and a 3-phase fault based on the ratio, and
implementing, using the protective action subsystem, the protective action based on identification of such a fault.
23 . The method of claim 13 , further comprising:
identifying, using the fault detection subsystem, a minimum phase current;
determining, using the fault detection subsystem, a magnitude of a phasor corresponding to the minimum phase current
determining, using the fault detection subsystem, an angle of the phasor corresponding to an angle of positive sequence voltage advanced by 90 degrees;
determining, using the fault detection subsystem, a refined ratio by subtracting the phasor from the ratio.
24 . The method of claim 23 , wherein the refined ratio compensates for the charging current of the electrical conductor.