# US 10,310,004 B2 · Time-domain differential line protection of electric power delivery systems

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- Number: US 10,310,004 B2
- Document ID: US10310004B2
- Status: Granted
- Kind: B2
- Application number: 15/269,904
- Filed: 2016-09-16
- Published: 2018-07-26
- Granted: 2019-06-04
- Earliest claimed: 2015-09-18
- Assignees: Schweitzer Engineering Laboratories, Inc.
- Applicants: Schweitzer Engineering Laboratories, Inc.
- Inventors: Edmund O. Schweitzer, III; Mangapathirao Venkata Mynam; David E. Whitehead; Bogdan Z. Kasztenny; Armando Guzman-Casillas; Veselin Skendzic
- Web page: https://patentgrep.com/patent/US10310004B2

## CPC

- G01R 31/11: using pulse reflection methods
- G01R 31/085: {in power transmission or distribution lines, e.g. overhead}
- H02H 1/0007: {concerning the detecting means (in general G01R or other subclasses of G01; reed switches H01H71/2445)}
- H02H 1/0092: {concerning the data processing means, e.g. expert systems, neural networks}
- H02H 3/083: {for three-phase systems}
- H02H 7/263: {involving transmissions of measured values (comparison of currents or voltages using pilot wires H02H3/30)}
- H02H 7/265: {making use of travelling wave theory}
- H04B 3/46: Monitoring; Testing
- G01R: MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES (indicating correct tuning of resonant circuits H03J3/12)
- H02H: EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS (indicating or signalling undesired working conditions G01R, e.g. G01R31/00, G08B; locating faults along lines G01R31/08; emergency protective devices H01H)
- H04B: TRANSMISSION

## Abstract

The present disclosure relates to detection of faults in an electric power system. In one embodiment, a time-domain traveling wave differential subsystem is configured to determine at a first terminal a first index between an arrival maximum of a traveling wave generated by a fault at the first terminal and an exit maximum of the traveling wave. The traveling wave subsystem also determines a second index between an arrival maximum of the traveling wave at the second terminal and an exit maximum of the traveling wave. An operating quantity and a restraint quantity may be determined based on a magnitude of the representations of electrical conditions in the first index and the second index. A fault may be declared based on a comparison of the operating quantity and the restraint quantity. A protective action subsystem may be configured to implement a protective action based on the declaration of the fault.

## Claims

### Claim 1

A system configured to detect a fault in a power line of an electric power delivery system, comprising:
a data acquisition subsystem in electrical communication with the power line of the electric power delivery system, configured to acquire a plurality of time-domain representations of electrical conditions at a plurality of index values in the electric power delivery system at each of a first terminal of the power line and a second terminal of the power line;
a time-domain traveling wave differential subsystem configured to determine:
a first maximum of a traveling wave generated by a fault at the first terminal and at a first index value based on the plurality of time-domain representations of electrical conditions;
a second maximum of the traveling wave at the second terminal and at a second index value based on the plurality of time-domain representations of electrical conditions;
a first exit window at the first terminal based on the second maximum, a propagation time between the first and second terminal and a variability margin;
a second exit window at the second terminal based on the first maximum, the propagation time between the first and second terminal and the variability margin;
a third maximum within the first exit window at a third time;
a fourth maximum within the second exit window at a fourth time;
a first index duration based on the first time and the third time;
a second index duration based on the second time and the fourth time;
an operating quantity based on a magnitude of the representations of electrical conditions in the first index and the second index;
a restraint quantity based on the magnitude of the representations of electrical conditions in the first index and the second index; and,
a fault detector subsystem configured to declare a fault based on a comparison of the operating quantity and the restraint quantity; and
a protective action subsystem configured to implement a protective action on the electric power delivery system based on the declaration of the fault.

### Claim 2 (depends on 1)

The system of claim 1, wherein the operating quantity is based on a summation of the magnitudes of the values in the first index and the second index.

### Claim 3 (depends on 1)

The system of claim 1, wherein the restraint quantity is based on a summation of the magnitudes of the values in the first index and the second index.

### Claim 4 (depends on 1)

The system of claim 1, wherein the data acquisition subsystem further comprises a differentiator smoother, and wherein the first index and the second index are processed by the differentiator smoother.

### Claim 5 (depends on 1)

The system of claim 1, wherein the differential subsystem is further configured to determine a fault location.

### Claim 6 (depends on 1)

The system of claim 1, wherein the fault detector subsystem further declares the fault based on a minimum pickup value.

### Claim 7 (depends on 6)

The system of claim 6, wherein the minimum pickup value varies based on the fault location.

### Claim 8 (depends on 1)

The system of claim 1, wherein the system is configured to monitor each phase of a three-phase power system and to identify the fault on at least one phase of the three-phase power system.

### Claim 9 (depends on 1)

The system of claim 1, wherein the fault detector subsystem is further configured to declare the fault based on the existence of an overcurrent condition.

### Claim 10 (depends on 9)

The system of claim 9, wherein the electric power delivery system comprises a multi-phase system, and the fault detector subsystem is further configured to declare the fault based on the existence of the overcurrent condition and the traveling wave on a phase of the multi-phase electric power system.

### Claim 11 (depends on 1)

The system of claim 1, wherein the variability margin is selected to compensate for at least one of a measurement error, a time synchronization error, and a sag in an electrical transmission line.

### Claim 12

A method for detecting a fault in an electric power delivery system, comprising:
acquiring a plurality of time-domain representations of electrical conditions at a plurality of index values in the electric power delivery system at each of a first terminal and a second terminal;
detecting a first maximum of a traveling wave generated by a fault at the first terminal and at a first index value based on the plurality of time-domain representations of electrical conditions;
detecting a second maximum of the traveling wave at the second terminal and at a second index value based on the plurality of time-domain representations of electrical conditions;
determining a first exit window at the first terminal based on the second maximum, a propagation time between the first and second terminal and a variability margin;
determining a second exit window at the second terminal based on the first maximum, the propagation time between the first and second terminal and the variability margin;
determining a third maximum within the first exit window at a third time;
determining a fourth maximum within the second exit window at a fourth time;
determining a first index duration based on the first time and the third time;
determining a second index duration based on the second time and the fourth time;
determining an operating quantity based on the representations of electrical conditions in the first index and the second index;
determining a restraint quantity based on the representations of electrical conditions in the first index and the second index; and,
declaring a fault based on a comparison of the operating quantity and the restraint quantity; and
implementing a protective action based on the declaration of the fault.

### Claim 13 (depends on 12)

The method of claim 12, wherein determining the operating quantity comprises summing the magnitudes of the values in the first index and the second index.

### Claim 14 (depends on 12)

The method of claim 12, wherein determining the restraint quantity comprises summing the magnitudes of the values in the first index and the second index.

### Claim 15 (depends on 12)

The method of claim 12, wherein the time-domain traveling wave differential subsystem further comprises a differentiator smoother, and wherein the first index and the second index are processed by the differentiator smoother.

### Claim 16 (depends on 12)

The method of claim 12, further comprising determining a fault location.

### Claim 17 (depends on 16)

The method of claim 16, wherein the fault detector subsystem further declares the fault based on a minimum pickup value.

### Claim 18 (depends on 17)

The method of claim 17, wherein the minimum pickup value varies based on the fault location.

### Claim 19 (depends on 12)

The method of claim 12, declaring the fault further comprises detecting an overcurrent condition.

### Claim 20 (depends on 12)

The method of claim 12, further comprising selecting the variability margin to compensate for at least one of a measurement error, a time synchronization error, and a sag in an electrical transmission line.