TRANSMISSION LINE FAULT LOCATION, ISOLATION & SYSTEM RESTORATION (FLISR) SYSTEM

Abstract

An electrical power network employing fault location, isolation and system restoration. The system includes a plurality of switching devices electrically coupled along a power line downstream of a fault interrupting device. The switching devices each have current and voltage sensing capability and the capability to provide pulse tests for detecting fault presence. The fault interrupting device performs reclosing operations, and when the plurality of switching devices detect fault presence a predetermined number of times in coordination with reclosing operations performed by the fault interrupting device and detect loss of voltage, each switching device opens. The fault interrupting device closes when the switching devices open, and the switching devices sequentially pulse test and close from a furthest upstream switching device when detecting return of voltage and no fault presence until a switching device closest to the fault pulse tests and detects fault presence and locks open.

Claims

1. A power restoration system for an electrical power network, the system comprising: a power line; at least one power source providing power to the power line; at least one fault interrupting device electrically coupled to the power line, the fault interrupting device being operable to detect fault current and perform reclosing operations; and a plurality of switching devices electrically coupled along the power line downstream of the at least one fault interrupting device, the plurality of switching devices each having current and voltage sensing capability, have the capability to provide pulse testing for detecting fault presence using a low energy pulse and have the same or similar opening response time, wherein in response to a fault on the power line, the at least one fault interrupting device performs reclosing operations, and when the plurality of switching devices detect fault current a predetermined number of times in coordination with reclosing operations performed by the fault interrupting device and detect loss of voltage when the at least one fault interrupting device opens again will open.

2. The system according to claim 1 wherein the at least one fault interrupting device closes when the plurality of switching devices are opened as a result of detecting the predetermined number of fault current passages, and wherein the plurality of the switching devices sequentially pulse test and close from a furthest upstream switching device when detecting return of voltage and no fault presence until a switching device closest to the fault pulse tests and detects fault presence and locks open.

3. The system according to claim 1 wherein the plurality of switching devices are not in communication with each other using an external communications system.

4. The system according to claim 1 wherein the plurality of switching devices are not fault interrupting devices.

5. The system according to claim 1 wherein the at least one power source is a first power source providing power to one end of the power line and a second power source providing power to another end of the power line and the at least one fault interrupting device is a first fault interrupting device at the one end of the power line and a second fault interrupting device at the another end of the power line.

6. The system according to claim 1 wherein the electrical power network is a medium voltage power distribution network.

7. The system according to claim 1 wherein the electrical power network is a high voltage power transmission network.

8. The system according to claim 1 wherein the at least one power source is an electrical substation.

9. A power restoration system for an electrical power transmission network, the system comprising: a transmission power line; a first substation providing high voltage power to one end of the power line; a second substation providing high voltage power to an opposite end of the power line; a first fault interrupting device electrically coupled to the one end of the power line, the first fault interrupting device being operable to detect fault current and perform reclosing operations; a second fault interrupting device electrically coupled to the opposite end of the power line, the second fault interrupting device being operable to detect fault current and perform reclosing operations; and a plurality of switching devices electrically coupled along the power line between the first and second fault interrupting devices, the plurality of switching devices each having current and voltage sensing capability, have the capability to provide pulse testing for detecting fault presence and have the same or similar opening response time, wherein in response to a fault on the power line, the first and second fault interrupting devices perform reclosing operations, and wherein when the plurality of switching devices detect fault current a predetermined number of times in coordination with reclosing operations performed by the fault interrupting devices and detect loss of voltage when the fault interrupting devices open following a reclose operation will open.

10. The system according to claim 9 wherein the fault interrupting devices close when the plurality of switching devices open, and wherein the plurality of the switching devices sequentially pulse test and close from a furthest upstream switching device when detecting return of voltage and no fault presence is detected until a switching device closest to the fault pulse tests and detects fault presence and locks open.

11. The system according to claim 9 wherein the plurality of switching devices are not in communication with each other using an external communications system.

12. The system according to claim 9 wherein the plurality of switching devices are not fault interrupting devices.

13. A method for restoring power in an electrical power network comprising: detecting fault current on a power line flowing from at least one power source to a fault by at least one fault interrupting device and a plurality of switching devices distributed along the power line, the switching devices each having current and voltage sensing capability, are capable of providing pulse tests for detecting fault presence and have the same or similar opening response time subject to the influences of load; performing reclosing by the at least one fault interrupting device to determine if the fault is still present; accumulating times that the plurality of switching devices detect fault current in response to the reclosing operations performed by the at least one fault interrupting device; opening all of the plurality of switching devices when the accumulated number of times reaches a predetermined number and detecting loss of voltage when the at least one fault interrupting device opens following a reclosing operation; closing the at least one fault interrupting device when the plurality of switching devices open; and sequentially pulse testing and closing the switching devices from a furthest upstream switching device when detecting return of voltage and no fault presence until a switching device closest to the fault pulse tests and detects fault presence and locks open.

14. The method according to claim 13 wherein the plurality of switching devices are not in communication with each other using an external communications system.

15. The method according to claim 13 wherein the plurality of switching devices are not fault interrupting devices.

16. The method according to claim 13 wherein detecting fault current on a power line includes detecting fault current on a power line flowing from a first power source at one end of the power line and a second power source at an opposite end of the power line, and wherein the at least one fault interrupting device is a first fault interrupting device at the one end of the power line and a second fault interrupting device at the another end of the power line.

17. The method according to claim 13 wherein the electrical power network is a medium voltage power distribution network.

18. The method according to claim 13 wherein the electrical power network is a high voltage power transmission network.

19. The method according to claim 13 wherein the at least one power source is an electrical substation.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0011] FIGS. 1 and 3-6 are simplified schematic type diagrams of an electrical power network that illustrates switch positions for a system and method for fault location, isolation and system restoration (FLISR);

[0012] FIG. 2 is a simplified block diagram of a switching device; and

[0013] FIG. 7 is a schematic type diagram of a high voltage electrical power transmission network that illustrates a system and method for FLISR.

DETAILED DESCRIPTION OF THE EMBODIMENTS

[0014] The following discussion of the embodiments of the disclosure directed to an electrical power network employing fault location, isolation and system restoration is merely exemplary in nature, and is in no way intended to limit the disclosure or its applications or uses.

[0015] FIG. 1 is a simplified schematic type diagram of an electrical power network 10, such as a radial medium voltage power distribution network operating between 12,000 and 38,000 volts, that illustrates a system and method for fault location, isolation and system restoration (FLISR). The network 10 includes an AC power source 12, such as an electrical substation that includes power transformers that step down high voltage power from a high voltage power line (not shown) to medium voltage, provided at one end of a feeder 14. A series of five switching devices 18, 20, 22, 24 and 26 are distributed along the feeder 14, where a fault interrupting device 16 is provided between the source 12 and the first switching device 18, and where the device 16 has reclosing capabilities. As used herein, the switching devices 18, 20, 22, 24 and 26 can be any suitable device, such as a pulse testing switching device, that are not in communication with each other, have current and voltage sensing capability and have the ability to test the circuit downline for fault presence using a pulse testing technique, but are not fault interrupting devices, where the switching devices 18, 20, 22, 24 and 26 have the same or similar opening response time subject to the influences of load. A feeder segment 28 is defined between the device 16 and the first switching device 18, a feeder segment 30 is defined between the switching devices 18 and 20, a feeder segment 32 is defined between the switching devices 20 and 22, a feeder segment 34 is defined between the switching devices 22 and 24, and a feeder segment 36 is defined between the switching devices 24 and 26.

[0016] FIG. 2 is a simplified block diagram of a switching device 40 intended to be a non-limiting representation of any one of the switching devices 18, 20, 22, 24 and 26, where the device 40 includes a switch 42, voltage/current sensors 44, a controller 46, a timer 48 and a buffer 66.

[0017] If a persistent fault 38 occurs in the line segment 34 it is desirable to open the switching devices 22 and 24 to isolate the fault 38 in the segment 34 so that power can be provided to the segments 28, 30 and 32 from the source 12 and possibly to the segment 36 from another source (not shown). When the fault 38 occurs, the device 16 and the switching devices 18, 20 and 22 detect the fault current flowing from the source 12 into the fault 38. When the device 16 detects the fault current it opens and then performs reclosing operations to determine if the fault 38 is still present. The switching devices 18, 20 and 22 are configured to accumulate in, for example, the buffer 66, the number of times that they detect the fault current in coordination with the number of times that the device 16 performs a reclosing operation, and will remain closed the first time that they detect fault current. When the accumulated number of times that the switching devices 18, 20 and 22 detect the fault current reaches a predetermined threshold, such as two, and then the switching devices 18, 20 and 22 detect loss of voltage when the device 16 opens the next time they will all open in unison, as shown in FIG. 3.

[0018] The device 16 then recloses again to test for the fault 38 and because the fault 38 is downstream of the switching device 18 and it is open, the device 16 does not detect fault current and remains closed. The switching device 18 then senses a return of voltage on its upstream side and pulse tests for the fault 38, as shown in FIG. 4. Because the fault 38 is downstream of the switching device 20 and it is open, the switching device 18 does not detect fault presence and closes. The switching device 20 then senses a return of voltage on its upstream side and pulse tests for the fault 38, as shown in FIG. 5. Because the fault 38 is downstream of the switching device 22 and it is open, the switching device 20 does not detect fault presence and closes. The switching device 22 then senses a return of voltage on its upstream side and pulse tests for the fault 38, as shown in FIG. 6. Because the fault 38 is in the segment 34, the switching device 22 detects the fault presence and locks open.

[0019] The system and method for FLISR as generally described above can be extended to high voltage transmission lines, such as 69,000 volts and higher. FIG. 7 is a schematic type diagram of an electrical power transmission network 50 that illustrates a system and method for FLISR showing this embodiment. The network 50 includes a large high voltage substation 52 having a pair of transformers 54 and 56 that down step extra high voltage, such as 345,000 volts, on lines 58 and 60, respectively, from a power plant (not shown) to high voltage provided on bus sections 62 and 64, respectively. circuit breakers 70 are connected between the bus sections 62 and 64 and control whether power is placed on high voltage transmission lines 72. Two circuit breakers 74 and 76 having reclosing and fault interrupting capabilities are connected to the bus sections 62 and 64 control the power placed on one end of a high voltage transmission line 78. The network 50 also includes a small high voltage substation 80 having a pair of transformers 82 and 84 that step down extra high voltage on lines 86 and 88, respectively, from a power plant (not shown) to high voltage provided on bus sections 90 and 92. Two circuit breakers 94 and 96 having reclosing and fault interrupting capability are connected to the bus sections 90 and 92 and control the power placed on the opposite end of the high voltage transmission line 78.

[0020] A series of four switching devices 100, 102, 104 and 106 are distributed along the line 78. As above, the switching devices 100, 102, 104 and 106 can be any suitable device, such as a switching device that has pulse testing capability, that are not in communication with each other, have current and voltage sensing capability and are capable of testing for continued fault presence using a low energy pulse, but do not have fault interrupting ratings, where the switching devices 100, 102, 104 and 106 have the same or similar opening response time subject to the influences of load. A line segment 108 is defined between the switching devices 100 and 102, a line segment 110 is defined between the switching devices 102 and 104, and a line segment 112 is defined between the switching devices 104 and 106. A medium voltage substation 114 is tapped off of the segment 108 and a medium voltage substation 116 is tapped off of the segment 112. The substations 114 and 116 each include a pair of fuses 120 and 122, a pair of transformers 124 and 126 that step down the high voltage to a medium voltage, and circuit breakers 128 that control the medium voltage power placed on feeders 130.

[0021] The system and method for FLISR that operates in the network 50 is similar to the system and method for FLISR that operates in the network 10. If a persistent fault occurs in the segment 110, the circuit breakers 74 and 76 and the switching devices 100 and 102 detect fault current from the substation 52 into the fault and the circuit breakers 94 and 96 and the switching devices 104 and 106 detect fault current from the substation 80 into the fault. When the circuit breakers 74 and 94, for example, detect the fault current they initially open and then perform reclosing operations to determine if the fault is still present. The switching devices 100, 102, 104 and 106 accumulate the number of times that the switching devices 100, 102, 104 and 106 detect fault current in coordination with the number of reclosing operations that are performed by the circuit breakers 74 and 94, where the first time they detect fault current they likely will remain closed. When the accumulated number of times that the switching devices 100, 102, 104 and 106 detect the fault current reaches a predetermined threshold, such as two, and then the switching devices 100, 102, 104 and 106 detect loss of voltage when the circuit breakers 74 and 94 open the next time they will all open.

[0022] When the circuit breakers 74 and 94 reclose the next time, they will not detect the fault current because the switching devices 100, 102, 104 and 106 are open, and will remain closed. When the switching devices 100 and 106 detect a return of voltage on their upstream side, they will pulse test and since the switching devices 102 and 104 are open they will not detect the fault presence and will close. When the switching devices 102 and 104 detect a return of voltage on their upstream side, they will pulse test closed and since the fault is in the section 110 they will detect the fault presence and will not close, and will then lock open. Thus, the fault is isolated in the section 110 and power is restored to the substations 114 and 116.

[0023] The foregoing discussion discloses and describes merely exemplary embodiments of the present disclosure. One skilled in the art will readily recognize from such discussion and from the accompanying drawings and claims that various changes, modifications and variations can be made therein without departing from the spirit and scope of the disclosure as defined in the following claims.