Fault-type identification in an electric power delivery system using composite signals

Patent metadata

Field	Value
Publication number	US-10859639-B2
Application number	US-201916404990-A
Country	US
Kind code	B2
Filing date	May 7, 2019
Priority date	Oct 2, 2018
Publication date	Dec 8, 2020
Grant date	Dec 8, 2020

Abstract

Fault-type identification using composite signals composed from symmetrical component voltages and currents is described herein. Angular differences between negative-sequence composite signals and zero-sequence composite signals are used to determine a single-line-to-ground fault, and the faulted phase. Angular differences between positive sequence voltage and negative-sequence composite signals are used to determine a multiple-line-to-ground fault, and the faulted phases. Negative-sequence composite signals and zero-sequence composite signals are calculated using combinations of negative-sequence currents and voltages and zero-sequence voltages and currents, respectively.

First claim

What is claimed is:

1. A system to determine a fault type in an electric power delivery system, comprising:
a signal processor to
obtain phase current and phase voltage signals from the electric power delivery system;
determine voltage phasors and current phasors of phase voltages and phase currents;
determine negative-sequence current from the current phasors, negative-sequence voltage from the voltage phasors, zero-sequence current from the current phasors, zero-sequence voltage from the voltage phasors, and positive-sequence voltage from the voltage phasors;
calculate a negative-sequence composite signal from the negative sequence current and voltage and a line impedance angle; and,
calculate a zero-sequence composite signal from the zero-sequence current and voltage and the line impedance angle;

a single-line-to-ground fault-type detector to:
calculate a single-line-to-ground angle using the negative-sequence composite signal and the zero-sequence composite signal;
determine a preliminary single-line-to-ground fault type;

a multiple-line fault-type detector to:
calculate a multiple-line-to-ground angle using the positive-sequence voltage and the negative-sequence composite signal;
determine a preliminary multiple-line fault type; and,

a fault-type identifier to:
determine a fault type based on the preliminary single-line-to-ground fault type, and the preliminary multiple-line fault type; and

a protective action module to effect a protective action using the determined fault type.

2. The system of claim 1 , wherein the negative-sequence composite signal comprises the negative-sequence current shifted by the line impedance angle but not the negative-sequence voltage when a loss-of-potential condition is detected on the electric power delivery system.

3. The system of claim 1 , wherein the zero-sequence composite signal comprises the zero-sequence current shifted by the line impedance angle but not the zero-sequence voltage when a loss-of-potential condition is detected on the electric power delivery system.

4. The system of claim 1 , wherein when a loss-of-potential condition is not detected on the electric power delivery system:
a forward negative-sequence composite signal comprises the negative-sequence current shifted by the line impedance angle less the negative-sequence voltage;
a reverse negative-sequence composite signal comprises the negative-sequence current shifted by the line impedance angle plus the negative-sequence voltage;
when a magnitude of the forward negative-sequence composite signal is greater than or equal to a magnitude of the reverse negative-sequence composite signal, then the negative-sequence composite signal comprises the forward negative-sequence composite signal and the zero-sequence composite signal comprises the zero-sequence current shifted by the line impedance angle less the zero-sequence voltage; and
when a magnitude of the forward negative-sequence composite signal is less than a magnitude of the reverse negative-sequence composite signal, then the negative-sequence composite signal comprises the reverse negative-sequence composite signal and the zero-sequence composite signal comprises the zero-sequence current shifted by the line impedance angle plus the zero-sequence voltage.

5. The system of claim 4 , wherein the negative-sequence voltage is multiplied by a negative-sequence coefficient and the zero-sequence voltage is multiplied by a zero-sequence coefficient.

6. The system of claim 1 , wherein the single-line-to-ground fault-type detector calculates the single-line-to-ground angle as:
angle( S 0)−angle( S 2)

where:
S0 is the zero-sequence composite signal; and
S2 is the negative-sequence composite signal.

7. The system of claim 1 , wherein the multiple-line-to-ground angle is a function of the negative-sequence composite signal and an angle shift.

8. The system of claim 1 , wherein the multiple line-to-ground angle is a function of the negative-sequence composite signal and a fault direction.

9. The system of claim 1 , wherein the multiple-line fault-type detector calculates the multiple-line-to-ground angle as:

angle
⁢

⁢

(

FDIR
*
V
⁢

⁢
1

S
⁢

⁢
2

)

+

45
⁢
°

-

Z
⁢

⁢
1
⁢
ANG

where:
FDIR is +1 for forward faults, and −1 for reverse faults;
S2 is the negative-sequence composite signal;
V1 is the positive-sequence voltage; and
Z1ANG is a positive-sequence line impedance angle.

10. The system of claim 1 , wherein the single-line-to-ground fault-type detector determines the preliminary single-line-to-ground fault type by comparing the single-line-to-ground angle against predetermined single-line-to-ground fault-type sectors.

11. The system of claim 1 , wherein the multiple-line-to-ground fault-type detector determines the preliminary multiple-line-to-ground fault type by comparing the multiple-line-to-ground angle against predetermined multiple-line-to-ground fault-type sectors.

12. The system of claim 1 , further comprising a supervisory signal comparator to compare signal magnitudes against predetermined thresholds before determining the fault type.

13. The system of claim 12 , wherein the signal magnitudes comprise magnitudes selected from the group consisting of: the positive-sequence voltage, negative-sequence current, zero-sequence current, negative-sequence composite signal, and zero-sequence composite signal.

14. The system of claim 12 , wherein the predetermined thresholds comprise absolute thresholds.

15. The system of claim 12 , wherein the predetermined thresholds comprise relative thresholds.

16. The system of claim 1 , wherein the fault type and faulted phases are determined based on the combination of preliminary single-line-to-ground fault type and the multiple-line-to-ground fault type.

17. The system of claim 1 , wherein the system further comprises a monitored equipment interface configured to signal protective equipment to open a faulted phase of the electric power delivery system based on the determined fault type.

18. A method to determine a fault type in an electric power delivery system, comprising:
obtaining phase current and phase voltage signals from the electric power delivery system;
determining voltage phasors and current phasors of the phase voltages and phase currents;
calculating negative-sequence current from the current phasors, negative-sequence voltage from the voltage phasors, zer

Assignees

• Schweitzer Engineering Lab Inc

Inventors

• Kasztenny Bogdan Z

Classifications

• G01R25/00

  Arrangements for measuring phase angle between a voltage and a current or between voltages or currents · CPC title

• H02H1/0007

  concerning the detecting means (in general G01R or other subclasses of G01; reed switches H01H71/2445) · CPC title

• G01R31/50 Primary

  Testing of electric apparatus, lines, cables or components for short-circuits, continuity, leakage current or incorrect line connections (testing of sparking plugs H01T13/58) · CPC title

• H02H7/26

  Sectionalised protection of cable or line systems, e.g. for disconnecting a section on which a short-circuit, earth fault, or arc discharge has occured (locating faults in cables G01R31/08) · CPC title

• G01R31/58

  Testing of lines, cables or conductors (testing of electric windings G01R31/72) · CPC title