Fault location system using voltage or current measurement from diverse locations on a distribution network

Patent metadata

Field	Value
Publication number	US-11378609-B2
Application number	US-202016827077-A
Country	US
Kind code	B2
Filing date	Mar 23, 2020
Priority date	Mar 25, 2019
Publication date	Jul 5, 2022
Grant date	Jul 5, 2022

Abstract

A method for identifying a location of a fault in an electrical power distribution network that includes identifying an impedance of an electrical line between each pair of adjacent utility poles, measuring a voltage and a current of the power signal at a switching device during the fault, and estimating a voltage at each of the utility poles downstream of the switching device using the impedance of the electrical line between the utility poles and the measured voltage and current during the fault. The method calculates a reactive power value at each of the utility poles using the estimated voltages, where calculating a reactive power value includes compensating for distributed loads along the electrical line that consume reactive power during the fault, and determines the location of the fault based on where the reactive power goes to zero along the electrical line.

First claim

What is claimed is:

1. A method for identifying a location of a fault in an electrical power distribution network, said network including a power source, at least one electrical line, a number of spaced apart utility poles supporting the at least one electrical line, and at least one switching device in the electrical line, said at least one switching device being operable to prevent a power signal from flowing through the switching device in response to detecting the fault, said method comprising:
identifying an impedance of the at least one electrical line between each pair of adjacent utility poles downstream of the at least one switching device;
measuring a voltage and a current of the power signal in the at least one switching device during the fault, but before the switching device prevents the power signal from flowing therethrough;
estimating a voltage at each of the utility poles downstream of the at least one switching device using the impedance of the electrical line between the utility poles and the measured voltage and current during the fault;
calculating a reactive power value at each of the utility poles using the estimated voltages, wherein calculating a reactive power value includes compensating for distributed loads along the electrical line that consume reactive power during the fault; and
determining the location of the fault based on where the reactive power value goes to zero along the at least one electrical line.

2. The method according to claim 1 wherein compensating for the distributed loads includes estimating the reactive power that the distributed loads consume based on a cumulative power rating size of a plurality of distribution transformers that provide power to the distributed loads downstream of the at least one switching device.

3. The method according to claim 2 wherein determining the cumulative power rating size of the transformers includes doing a graph search of all of the transformers downstream of the at least one switching device, and adding the sizes together.

4. The method according to claim 2 wherein compensating for the distributed loads includes determining a prefault power value from a measured current and voltage by the at least one switching device before the fault, determining a utilization ratio that is the prefault power value divided by the cumulative transformer size, calculating a nominal load power value at each of the utility poles that includes a transformer as the utilization ratio multiplied by the size of the transformer on that pole, using the estimated voltage and the nominal load power value at the pole to determine a fault load power value during the fault, dividing the fault load power value by the estimated voltage to obtain a current draw value at the pole, and cumulatively reducing the current that is used to estimate the voltage at each pole based on the current draw value used to supply the loads.

5. The method according to claim 4 wherein determining the fault load power value during the fault includes using the equation:

P
fault

=

(

v

f
⁢
a
⁢
u
⁢
l
⁢
t

v

nom
⁢

⁢
inal

)

n

⁢

P
prefault

where P fault is the fault load power value, P prefault is the prefault power value, v fault is the measured voltage at the fault location during the fault, v nominal is the voltage before the fault, and n is an exponential that is determined by experimentation, where n=2 for constant impedance, n=1 for constant current and n=0 for constant power.

6. The method according to claim 1 wherein calculating a reactive power value includes compensating for a capacitor provided in the electrical line downstream of the at least one switching device that provides reactive power on the electrical line.

7. The method according to claim 6 wherein compensating for the capacitor includes calculating a fault power at the capacitor.

8. The method according to claim 1 wherein estimating the voltage at each pole includes using the equation:
Q =imag( I*V )
where Q is reactive power, I is the measured fault current and V is the estimated voltage.

9. The method according to claim 1 wherein identifying the fault location includes identifying the location of the fault in a span between utility poles using the equation:
Q=lX line/mile I 2
where Q is the estimated reactive power at the last utility pole before the fault location, I is the fault current, X is the inductive component of the line impedance Z, and l is the distance from the at least one switching device to the fault location.

10. The method according to claim 1 wherein the power source is an electrical substation and the electrical power distribution network is a medium voltage power distribution network.

11. The method according to claim 1 wherein the at least one switching device is a recloser.

12. The method according to claim 1 wherein the at least one electrical line is one phase of three-phase lines in a feeder line.

13. A method for identifying a location of a fault in an electrical power distribution network, said network including a substation, a feeder line, a number of spaced apart utility poles supporting the feeder line, and a recloser in the feeder line on one of the poles, said recloser being operable to prevent a power signal from flowing through the recloser in response to detecting the fault, said method comprising:
identifying an impedance value of the feeder line between each pair of adjacent utility poles downstream of the recloser;
measuring a voltage and a current of the power signal in the recloser during the fault, but before the recloser prevents the power signal from flowing therethrough;
estimating a voltage at each of the utility poles downstream of the recloser using the impedance of the feeder line between the utility poles and the measured voltage and current during the fault;
calculating a reactive power value at each of the utility poles using the estimated voltages, wherein calculating the reactive power value includes compensating for distributed loads along the feeder line downstream of the recloser that consume reactive power during the fault based on a cumulative power rating size of a plurality of distribution transformers that provide power to the distributed loads; and
determining the location of the fault based on where the reactive power value goes to zero along the feeder line.

14. The method according to claim 13 wherein compensating for the distributed loads includes determining a prefault powe

Assignees

• S & C Electric Co

Inventors

• Sharon Yoav

Classifications

• Y04S10/52

  Outage or fault management, e.g. fault detection or location · CPC title

• G01R21/003

  Measuring reactive component · CPC title

• H02H3/40

  responsive to ratio of voltage and current · CPC title

• H02H7/261

  involving signal transmission between at least two stations (transmission of signals in general H02H1/0061) · CPC title

• G01R31/62

  Testing of transformers · CPC title