Fault Location, Isolation and System Recovery (FLISR) System

Abstract

The present invention provides a power network employing fault location, isolation and system restoration. The system also includes a plurality of switching devices electrically coupled along the power line downstream of the fault circuit breaker. Each switching device has a current and voltage sensing function and a pulse test function to detect the presence of a fault. The fault circuit breaker performs a reclosing operation, and in conjunction with the reclosing operation, the plurality of switching devices perform a predetermined number of fault current detections and each switching device opens when a loss of voltage is detected. When the switching device opens, the fault circuit breaker closes, and the plurality of switching devices then perform a pulse test, and when a return of voltage is detected and the presence of a fault is not detected, the switching device most upstream closes, and the pulse tests are performed continuously until the switching device closest to the fault performs a pulse test, detects the presence of a fault, and is locked in the open position.

Description

[Technical field]

[0001] (CROSS REFERENCE TO RELATED APPLICATIONS) This application claims the benefit of priority to U.S. Provisional Patent Application No. 63 / 232,318, filed August 12, 2021, the entire disclosure of which is expressly incorporated by reference herein for all purposes.

[0002] The present invention relates generally to power networks employing fault location and isolation systems. [Background technology]

[0003] Electricity networks, often referred to as power systems, typically include power plants with generators such as gas turbines, nuclear reactors, coal-fired generators, and hydroelectric dams. Power plants provide electricity at various medium voltages, which are stepped up by transformers to high voltage AC signals and connected to high voltage transmission lines that feed power to substations, usually located in a geographical area, where they are stepped down to medium voltages by transformers for distribution. Substations provide medium voltage power to three-phase feeders, including three single-phase feeders, which provide medium voltage to various distribution transformers and siding connections. Three-phase and single-phase sidings branch off from the feeders that provide medium voltage to various distribution transformers, where the voltage is stepped down to lower voltages for distribution to loads such as homes and businesses. The above types of electricity distribution networks typically include switching devices, circuit breakers, reclosers, interrupters, etc., that control the flow of power through the network.

[0004] Periodically, faults occur in electricity supply networks due to various factors, such as animals touching electric wires, lightning strikes, falling branches on electric wires, vehicles crashing into utility poles, etc. If such faults cause short circuits and increase the load on the network, the current flow from the substation can increase significantly along the fault path, e.g. many times higher than normal. This amount of current can significantly heat up and even melt the electric wires, and even cause mechanical damage to various components in the substation and the network. In many cases, such faults are not persistent or permanent, but temporary or intermittent, and the cause of the fault, e.g. a lightning strike, is removed shortly after the fault occurs and the supply network starts working normally almost immediately.

[0005] Fault interrupters, such as reclosers employing vacuum circuit breakers, are provided on poles or underground circuits along the power line, with the recloser having a switch that allows or prevents the flow of power downstream. The recloser monitors the current flow by detecting current and voltage in the feeder and includes a control device that indicates a problem in the network circuit, such as detecting a high current during a fault event. When such a high fault current is detected, the recloser opens in response and then closes after a short delay to determine whether the fault still exists. If a fault current flows when the recloser is closed after opening, the recloser immediately resumes according to a preset timing. If a fault current indicating a sustained fault is detected twice or more times during subsequent opening and closing operations, the recloser remains open, and the inspection interval may be increased with each inspection. A typical reclosing operation for fault detection testing involves passing the fault current through the recloser for approximately 3-6 cycles or 50-100 milliseconds before the recloser opens, but a delay curve test may allow the fault current to flow for a much longer period, potentially causing significant stress to various equipment in the network.

[0006] To solve the above problems, the art has developed fault interrupters using pulse testing techniques, where for example vacuum interrupter contacts are pulsed so that the full fault current of several fundamental frequency cycles is not applied to the network while the reclosing device determines if the fault is still present. Typically the pulse is approximately one-half of a fundamental frequency current cycle, and furthermore such fault interrupters close at an appropriate point on the voltage waveform, eliminating asymmetric currents and reducing stress on network equipment due to high currents.

[0007] When a fault is detected, it is desirable for the first fault circuit breaker upstream of the fault to open as quickly as possible so that the fault can be quickly removed from the network to prevent equipment damage, personal injury, fire, etc., and so that the loads upstream of the fault circuit breaker are not disconnected from the supply and service to the loads is not interrupted. Furthermore, if for some reason the first fault circuit breaker upstream of the fault fails to open, it is desirable for the next fault circuit breaker upstream of the fault to open. To achieve this, some type of communication or coordinated protection scheme needs to be employed in the network so that the desired fault circuit breaker is opened in response to the fault.

[0008] A sectionalizer is a self-contained circuit-opening device that is typically used in conjunction with a source-side protection device, such as a recloser or circuit breaker, to automatically isolate a faulted section of an electrical distribution network. Sectionals are typically distributed among reclosers to provide a system for isolating smaller sections of the network in response to a fault. Sectionals also typically observe the presence or absence of a series of fault currents and voltages to indicate the presence of a fault, or count a number of reclose attempts, isolating the circuit by opening energized contacts within the device when a predefined number of reclose attempts has been reached. Existing electrical distribution circuit sectionalizers detect the passage of fault current, including both an initial fault event and a subsequent recloser initiation event, as part of a more sophisticated fault isolation and restoration process. These processes may include counting discrete intervals of fault current passage or counting discrete intervals of the presence or absence of voltage. Equipment or devices that recognize pulse inspection operations require sensors and controls capable of measuring current and / or voltage and implementing pulse recognition algorithms. Summary of the Invention [Problem to be solved by the invention]

[0009] (There is no description in the text that corresponds to the problem that the invention is trying to solve.) [Means for solving the problem]

[0010] A power network with fault location, isolation and system restoration is disclosed and described below. The power network includes a power line, at least one power source providing power to the power line, and a fault interrupter electrically coupled to the power line. The fault interrupter detects a fault current and performs a reclosing operation to check whether the fault still exists. The power network also includes a plurality of switching devices electrically coupled along the power line downstream from the fault interrupter. Each switching device has current and voltage sensing capabilities, a capability to use a low energy pulse to check whether the fault still exists, and the same or similar opening response time under the influence of a load. In response to a fault on the power line, the fault interrupter performs a reclosing operation, and each of the plurality of switching devices accumulates a number of times that it detected a fault current as a result of the reclosing operation. When a predetermined number of accumulated times, such as 2, is reached and a loss of voltage is detected as a result of the fault interrupter opening, the plurality of switching devices open. When the plurality of switching devices open, the fault interrupter does not detect a fault and closes. The multiple switching devices then perform pulse testing, closing first in response to detection of an upstream voltage and non-detection of a downstream fault current, followed by the switching device closest to the fault, and so on until it detects the presence of a fault and is locked in the open position.

[0011] Further features of the present disclosure will become apparent from the following description and claims, taken in conjunction with the accompanying drawings. [Brief description of the drawings]

[0012] [Figure 1] FIG. 1 is a simplified wiring diagram of a power network showing the placement of switches of a Fault Location, Isolation and System Recovery (FLISR) system and method. [Diagram 2] FIG. 2 is a simplified block diagram of a switching device. [Diagram 3] FIG. 1 is a simplified wiring diagram of a power network showing the placement of switches of the FLISR system and method. [Figure 4] FIG. 1 is a simplified wiring diagram of a power network showing the placement of switches of the FLISR system and method. [Diagram 5] FIG. 1 is a simplified wiring diagram of a power network showing the placement of switches of the FLISR system and method. [Figure 6] FIG. 1 is a simplified wiring diagram of a power network showing the placement of switches of the FLISR system and method. [Figure 7] 1 is a schematic diagram of a high voltage power transmission network illustrating the FLISR system and method; DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] The following description of disclosed embodiments of a power network employing fault location, isolation, and system restoration is merely exemplary in nature and is not intended to limit the disclosure, its application, or uses.

[0014] 1 is a simplified electrical distribution diagram of an electrical power network 10, such as a radial medium voltage distribution network operating at 12,000-38,000 volts, illustrating a system and method for fault location, isolation and system restoration (FLISR). The network 10 includes an AC power source 12, such as a substation at one end of a feeder 14, the substation including a power transformer that steps down high voltage power from a high voltage power line (not shown) to a medium voltage. Five switching devices 18, 20, 22, 24, 26 are distributed along the feeder 14, with a fault interrupter 16 between the source 12 and the first switching device 18, the fault interrupter having a reclosing function. The switching devices 18, 20, 22, 24, 26 used herein do not communicate with each other, have current and voltage sensing capabilities, and have the capability of testing the circuit downline for faults using pulse testing techniques, but are not fault interrupters and can be any suitable devices, such as pulse testing switching devices, and have the same or similar opening response times under the influence of a load. A feeder section 28 is defined between the fault interrupter 16 and the first switching device 18, a feeder section 30 is defined between the switching devices 18, 20, a feeder section 32 is defined between the switching devices 20, 22, a feeder section 34 is defined between the switching devices 22, 24, and a feeder section 36 is defined between the switching devices 24, 26.

[0015] FIG. 2 is a simplified block diagram of a switching device 40, intended as a non-limiting replica of any one of switching devices 18, 20, 22, 24, 26, which includes a switch 42, a voltage / current sensor 44, a controller 46, a timer 48, and a buffer 66.

[0016] In the event of a persistent fault 38 occurring in feeder section 34, switching devices 22 and 24 desirably open to isolate fault 38 in feeder section 34 and allow power to be provided from power source 12 to feeder sections 28, 30, 32 and, potentially, from another power source (not shown) to feeder section 36. When fault 38 occurs, fault interrupter 16 and switching devices 18, 20, 22 detect a fault current flowing from power source 12 to fault 38. When fault interrupter 16 detects the fault current, it opens and then performs a reclosing operation to determine whether fault 38 is still present. Switching devices 18, 20, 22 are configured to store the number of times the fault current has been detected in conjunction with the number of reclosing operations performed by fault interrupter 16, e.g., in buffer 66, and remain closed the first time the fault current is detected. If the cumulative number of times that the switching devices 18, 20, 22 detect a fault current reaches a predetermined threshold, such as two, and the switching devices 18, 20, 22 then detect a loss of voltage when the fault interrupter 16 opens, the switching devices 18, 20, 22 will open simultaneously, as shown in FIG. 3.

[0017] The fault interrupter 16 then closes again to check for the fault 38, but since the fault 38 is downstream of the switching device 18 and the switching device 18 is open, the device 16 does not detect the fault current and remains closed. The switching device 18 then detects a voltage return on its upstream side and performs a pulse check for the fault 38, as shown in FIG. 4. Since the fault 38 is downstream of the switching device 20 and the switching device 20 is open, the switching device 18 does not detect the presence of a fault and closes. The switching device 20 then detects a voltage return on its upstream side and performs a pulse check for the fault 38, as shown in FIG. 5. Since the fault 38 is downstream of the switching device 22 and the switching device 22 is open, the switching device 20 does not detect the presence of a fault and closes. The switching device 22 then detects a voltage return on its upstream side and performs a pulse check for the fault 38, as shown in FIG. 6. Since the fault 38 is present in the feeder section 34, the switching device 22 detects the presence of a fault and is locked in the open position.

[0018] In general, the FLISR system and method as described above can be applied to high voltage transmission lines up to 69,000 volts or higher. FIG. 7 is a wiring diagram of a power transmission network 50 illustrating the FLISR system and method according to the present embodiment. The network 50 includes a large high voltage substation 52 having a pair of transformers 54, 56 that step down an extra high voltage, such as 345,000 volts, supplied from a generating station (not shown) to transmission lines 58, 60, respectively, to a high voltage supplied to bus sections 62, 64, respectively. A circuit breaker 70 is connected between the bus sections 62 and 64 to control whether power is flowing to the high voltage transmission line 72. Two circuit breakers 74, 76 with reclosing and fault interrupting functions are connected to the bus sections 62, 64 to control the power flowing to one end of the high voltage transmission line 78. Network 50 also includes a miniature high voltage substation 80 having a pair of transformers 82, 84 that step down the extra high voltage supplied from a generating station (not shown) on transmission lines 86, 88, respectively, to a high voltage supplied on bus sections 90, 92, respectively. Two circuit breakers 94, 96 with reclosing and fault interrupting capabilities are connected to bus sections 90, 92 and control the power flowing to the other end of high voltage transmission line 78.

[0019] A series of four switching devices 100, 102, 104, 106 are distributed along the transmission line 78. As noted above, the switching devices 100, 102, 104, 106 do not communicate with each other, may be any suitable devices, such as switching devices that have current and voltage sensing capabilities and the ability to continuously test for faults using low energy pulses, but do not have a fault interrupting rating, and have the same or similar opening response times under the influence of a load. A transmission line segment 108 is defined between the switching devices 100, 102, a transmission line segment 110 is defined between the switching devices 102, 104, and a transmission line segment 112 is defined between the switching devices 104, 106. A medium voltage substation 114 branches off from transmission line section 108, and a medium voltage substation 116 branches off from transmission line section 112. Each of the medium voltage substations 114, 116 includes a pair of fuses 120, 122, a pair of transformers 124, 126 that step down the high voltage to a medium voltage, and a circuit breaker 128 that controls the medium voltage power flowing through a feeder 130.

[0020] The FLISR system and method implemented in network 50 is similar to the FLISR system and method implemented in network 10. In the event of a sustained fault on transmission line section 110, circuit breakers 74, 76 and switching devices 100, 102 detect the fault current flowing from substation 52 to the fault, and circuit breakers 94, 96 and switching devices 104, 106 detect the fault current flowing from substation 80 to the fault. For example, when circuit breakers 74, 94 detect the fault current, they first open and then perform a reclose operation to determine if the fault still exists. The switching devices 100, 102, 104, 106 accumulate the number of times they detect the fault current in conjunction with the number of reclose operations performed by circuit breakers 74, 94 and remain closed the first time they detect the fault current. If the cumulative number of times that the switching devices 100, 102, 104, 106 detect a fault current reaches a predetermined threshold, such as two, and the switching devices 100, 102, 104, 106 then detect a loss of voltage when the circuit breakers 74, 94 open, the switching devices 100, 102, 104, 106 all open.

[0021] The circuit breakers 74, 94 then close again and the switching devices 100, 102, 104, 106 are open so the circuit breakers 74, 94 do not detect a fault current and remain closed. When the switching devices 100, 106 then detect the return of voltage on their respective upstream sides, they perform a pulse check and because the switching devices 102, 104 are open, the switching devices 100, 106 do not detect the presence of a fault and close. When the switching devices 102, 104 then detect the return of voltage on their respective upstream sides, they perform a pulse check and because a fault is present on the line section 110, the switching devices 102, 104 detect the presence of a fault and do not close but are locked open. In this manner, the fault is isolated at the line section 110 and power is restored to the substations 114, 116.

[0022] The foregoing disclosure discloses and describes merely exemplary embodiments of the present invention. Those skilled in the art will readily recognize from the above description and the accompanying drawings and claims that various changes, modifications, and variations can be made without departing from the spirit and scope of the present disclosure, as defined in the following claims. [Explanation of symbols]

[0023] 10. Electricity Network 12 AC power supply 14, 130 feeder line 16 Fault Circuit Breaker 18, 20, 22, 24, 26, 40, 100, 102, 104, 106 Switching device 28, 30, 32, 34, 36 Power supply section 38 Malfunction 42 Switch 44 Voltage / Current Sensor 46 Control device 48 Timer 50 Power Transmission Network 52 Large high-voltage substation 54, 56, 82, 84, 124, 126 Transformers 58, 60, 86, 88 Power Lines 62, 64, 90, 92 bus sections 66 buffers 70, 74, 76, 94, 96, 128 Circuit Breakers 72, 78 High voltage power lines 80 Small high-voltage substation 108, 110, 112 Transmission line sections 114, 116 Medium voltage substation 120, 122 fuse

Claims

1. A power restoration system for a power network, wherein the power restoration system includes a power line, at least one power source that supplies power to the power line, at least one circuit breaker that is electrically coupled to the power line and detects a fault current to perform a reclosing operation, a plurality of switching devices that are electrically coupled along the power line on the downstream side of the at least one circuit breaker, each of the plurality of switching devices having a current / voltage detection function, a function of performing a pulse inspection to detect the presence of a fault using a low-energy pulse, and having the same or similar opening response time and is provided with. In response to a fault in the power line, the at least one circuit breaker performs a reclosing operation, and in conjunction with the reclosing operation performed by the at least one circuit breaker, the plurality of switching devices detect the fault current a predetermined number of times. When the plurality of switching devices detect a voltage loss when the at least one circuit breaker opens, the plurality of switching devices open again, when the plurality of switching devices open as a result of detecting the fault current the predetermined number of times, the at least one circuit breaker closes, the plurality of switching devices perform a pulse inspection, and when the return of the voltage is detected and the presence of a fault is not detected, it closes from the uppermost switching device, the switching device closest to the fault performs a pulse inspection, and the pulse inspection is continuously performed until the presence of a fault is detected and it is locked in the open state. A power restoration system characterized by this.

2. The power restoration system according to claim 1, wherein the plurality of switching devices do not communicate with each other using an external communication system.

3. The power restoration system according to claim 1, wherein the plurality of switching devices are not circuit breakers.

4. The at least one power source is a first power source that supplies power to one end of the power line and a second power source that supplies power to the other end of the power line, and the at least one circuit breaker is a first circuit breaker at the one end of the power line and a second circuit breaker at the other end of the power line. The power restoration system according to claim 1, characterized by this.

5. The power restoration system according to claim 1, wherein the power network is a medium-voltage distribution network.

6. The power restoration system according to claim 1, wherein the power network is a high-voltage power transmission network.

7. The power restoration system according to claim 1, wherein the at least one power source is a substation.

8. A power restoration system for a power transmission network, wherein the power restoration system comprises: A power transmission line; A first substation that supplies high-voltage power to one end of the power transmission line; A second substation that supplies high-voltage power to the other end of the power transmission line; A first circuit breaker electrically connected to the one end of the power transmission line, detecting a fault current and performing a reclosing operation; A second circuit breaker electrically connected to the other end of the power transmission line, detecting a fault current and performing a reclosing operation; A plurality of switching devices electrically connected along the power transmission line between the first and second circuit breakers, each of the plurality of switching devices having a current / voltage detection function, a function of performing a pulse inspection to detect the presence of a fault, and a switching device having the same or similar opening response time And the first and second circuit breakers perform a reclosing operation in response to a fault in the power transmission line, and in conjunction with the reclosing operation performed by the circuit breakers, the plurality of switching devices detect a fault current a predetermined number of times. When the plurality of switching devices detect a voltage loss when the circuit breakers open after the reclosing operation, the plurality of switching devices open again. When the plurality of switching devices open, the circuit breakers close, the plurality of switching devices perform a pulse inspection, and when the return of the voltage is detected and the presence of a fault is not detected, the plurality of switching devices close from the uppermost upstream switching device, and the switching device closest to the fault performs a pulse inspection. A power restoration system characterized in that the pulse inspection is continuously performed until the presence of a fault is detected and the device is locked in an open state.

9. The power restoration system according to claim 8, wherein the plurality of switching devices do not communicate with each other using an external communication system.

10. The power restoration system according to claim 8, wherein the plurality of switching devices are not circuit breakers.

11. A power restoration method in a power network, comprising: At least one circuit breaker and a plurality of switching devices distributed along the power line detect a fault current of the power line flowing from at least one power source to a fault, wherein each of the plurality of switching devices has a current / voltage detection function, has a function of performing a pulse inspection for detecting the presence of a fault, and has the same or similar opening response time under the influence of a load. The step of performing a reclosing operation by the at least one circuit breaker and determining whether a fault still exists. A step of accumulating the number of times the plurality of switching devices detect a fault current in response to the reclosing operation performed by the at least one circuit breaker. When the accumulated number reaches a predetermined number, all of the plurality of switching devices are opened, and when the at least one circuit breaker is opened after the reclosing operation, the plurality of switching devices detect a voltage loss. A step of closing the at least one circuit breaker when the plurality of switching devices are opened. The plurality of switching devices perform a pulse inspection, close from the uppermost upstream switching device when no voltage return is detected and no fault is detected, the switching device closest to the fault performs a pulse inspection, detects the presence of a fault, and continuously performs a pulse inspection until it is locked in an open state. A power restoration method characterized by including the above.

12. The power restoration method according to claim 11, characterized in that the plurality of switching devices do not communicate with each other using an external communication system.

13. The power restoration method according to claim 11, characterized in that the plurality of switching devices are not circuit breakers.

14. The step of detecting a fault current of the power line includes detecting a fault current of the power line flowing from a first power source at one end of the power line and a second power source at the other end of the power line, and the at least one circuit breaker is a first circuit breaker at the one end of the power line and a second circuit breaker at the other end of the power line. The power restoration method according to claim 11, characterized by this.

15. The power restoration method according to claim 11, characterized in that the power network is a medium voltage distribution network.

16. The power restoration method according to claim 11, characterized in that the power network is a high voltage transmission network.

17. The power restoration method according to claim 11, wherein the at least one power source is a substation.

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