Method for locating and isolating a fault in a power distribution network

Patent metadata

Field	Value
Publication number	US-11719736-B2
Application number	US-202117501136-A
Country	US
Kind code	B2
Filing date	Oct 14, 2021
Priority date	Dec 7, 2020
Publication date	Aug 8, 2023
Grant date	Aug 8, 2023

Abstract

A method for fault location and isolation in a power distribution network, where the network includes a plurality of switching devices provided along a feeder, and at least one of the switching devices does not have voltage sensing capabilities. The method includes detecting an overcurrent event in the network from the fault and interrupting the overcurrent event by opening and then immediately locking out or subsequently reclosing and testing the fault. A count value is increased in each switching device that detected the overcurrent event. A message is sent from each of the switching devices that detected the overcurrent event and then detected the loss of voltage upstream to an upstream neighbor switching device. Current measurements in the messages, measured current by the devices and the counts values in the devices determine what devices are opened to isolate the fault.

First claim

What is claimed is:

1. A method for locating and isolating a fault in a power distribution network, the network including at least one power source, at least one feeder and a plurality of switching devices positioned along the at least one feeder and being in communications with each other, where network sections are defined between adjacent switching devices and where all of the switching devices have overcurrent sensing capability and at least one of the switching devices does not have a voltage sensing capability, the method comprising:
detecting an overcurrent event in the network from the fault by at least some of the switching devices;
interrupting the overcurrent event by opening and then immediately locking out or performing subsequent reclosing operations by a switching device of the at least some of the switching devices that detected the overcurrent event;
increasing a count value in the switching device of the at least some of the switching devices that detected and interrupted the overcurrent event, in each of the switching devices that detected the overcurrent event and then detected loss of voltage upstream, in each of the switching devices that detected the overcurrent event and does not have a voltage sensing capability, and in each of the switching devices that detected the overcurrent event but does not have a voltage sensing capability and inferred a loss of voltage upstream by measured current;
sending a count and current (C&I) message from the each of the switching devices that detected the overcurrent event and then detected the loss of upstream voltage, from the each of the switching devices that detected the overcurrent event and has an upstream neighbor switching device that does not have a voltage sensing capability, from the each of the switching devices that detected the overcurrent event and does not have a voltage detecting capability, and from the each of the switching devices that detected the overcurrent event but does not have a voltage detecting capability and inferred loss of voltage upstream by measured current, the C&I message including a current locally measured by the sending switching devices and a count value of the sending switching devices;
starting a C&I timer in the each of the switching devices that sent a C&I message;
performing a current matching test, in each of the switching devices in which the C&I timer has expired, between the measured current received in a C&I message by that switching device and a current measured by that switching device;
populating a fault isolation table in the each switching device that detects the overcurrent event that includes its count value, its measured current and accumulated current from a received C&I message;
repeating interrupting the overcurrent event, increasing the count value, sending the C&I messages, starting the C&I timer, performing the current matching test and populating the fault isolation table;
determining that the fault is in an immediate downstream section of one of the switching devices based on the count value in the one of the switching devices matching a predetermined first count value and a current matching test failure; and
sending a downstream switch open message to an immediate downstream switching device from the one of the switching devices that determined that the fault is in the immediate downstream section to isolate a downstream end of the immediate downstream section.

2. The method according to claim 1 further comprising sending an upstream switch open message to a downstream switching device to open the switching device from a sending switching device that has a count value matching a predetermined second count value and if the sending switching device has a voltage sensing capability and detects an upstream loss of voltage, the sending switching device does not have a voltage sensing capability and did not open to interrupt the overcurrent event, the switching device is a sectionalizer, and if the sending switching device is capable of interrupting the overcurrent event, does not have a voltage sensing capability and inferred the loss of voltage from measured current, wherein the first count value is less than the second count value.

3. The method according to claim 2 further comprising locking open the switching device that detected the over current event when the count value in the switching device matches a predetermined third count value, wherein the third count value is greater than the second count value, and wherein the switching device ignores the upstream switch open message if it receives it, and opens if the count matches and if there is upstream loss-of-voltage (LoV).

4. The method according to claim 1 further comprising sending an information message containing fault location information from the switching device that determined that the fault is in its-the immediate downstream section.

5. The method according to claim 4 further comprising sending a power restoration request message following isolation of a faulted section using the fault location information from the information message.

6. The method according to claim 1 wherein inferring the loss of voltage by the switching devices that do not have a voltage sensing capability includes determining that a current was below a current threshold before the overcurrent event.

7. The method according to claim 1 wherein inferring the loss of voltage by the switching devices that do not have a voltage sensing capability includes comparing a measured current before the overcurrent event and after the overcurrent event.

8. The method according to claim 7 wherein inferring the loss of voltage by the switching devices that do not have a voltage sensing capability includes determining that the measured current before the overcurrent event was above a current threshold, then determining that the measured current dropped below the current threshold after the overcurrent event.

9. The method according to claim 1 wherein one of the switching devices detects a return to a healthy voltage and knows that its upstream neighbor device has a voltage sensor deduces that an upstream switching device also detects the return to healthy voltage.

10. The method according to claim 1 wherein performing a current matching test includes computing a difference between the measured current by one of the switching devices and accumulated current from C&I messages received by the one switching device.

11. The method according to claim 1 wherein each device has a loss-of-voltage (LoV) Boolean indicator, which is stored separately from the fault isolation table, which holds the state of whether the switching device detected upstream LoV after the overcurrent event was interrupted.

12. The method according to claim 1 wherein the switching devices are coordinated where the switching device that interrupts the overcurrent event is a switching device located closest upstream of the fault having fault interrupting capabilities.

13. The method according to claim 1 wherein the switching devices are mis-coordinated where the switching device that interrupts the overcurrent event is switching device not located closest upstream of the fault having fault interrupting capabilities.

14. The method according to claim 1 wherein the method locates and isolates multiple sequential faults, multiple simultaneous faults and galloping faults.

15. The method according to claim 1 wherein the network is designed to support unlimited segmentation with sectionalizers or reclosers.

16. The method according to claim 1 wherein the network is a closed-loop network.

Assignees

• S & C Electric Co

Inventors

• Marendic Boris
• Sharon Yoav

Classifications

• G01R31/086 Primary

  in power transmission or distribution networks, i.e. with interconnected conductors · CPC title

• H02H3/063

  Details concerning the co-operation of many similar arrangements, e.g. in a network (sectionalised protection H02H7/26) · CPC title

• H02H7/261

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

• G01R31/08 Primary

  Locating faults in cables, transmission lines, or networks · CPC title

• G01R31/085 Primary

  in power transmission or distribution lines, e.g. overhead · CPC title