Disconnection detection system, current state measuring device, disconnection detection method, and disconnection detection program

Abstract

To provide a disconnection detection system capable of detecting a disconnection by a relatively simple composition.SOLUTION: A disconnection detection system 1 according to one aspect of the present invention comprises: a plurality of current measurers 11 for respectively measuring waveforms of three-phase currents and disposed in a trunk line 110 of a three-phase AC power distribution network 100, which includes the trunk line 110 and branch lines 120 branching from the trunk line 110, across a branch point of at least one branch line 120; a phase difference calculator 12 for calculating a mutual phase difference of the three-phase currents on the basis of the waveforms measured by the current measurers 11; and a disconnection estimator 22 for estimating that a disconnection has occurred when the phase difference calculated by the phase difference calculator 12 changes.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a wire break detection system, a current state measuring device, a wire break detection method, and a wire break detection program. [Background technology]

[0002] Conventionally, a break in the main line of a 6.6kV three-phase high-voltage distribution line, for example, is detected by the occurrence of a power outage and a change in voltage measured by a sensor switch installed on the main line, and the location of the break is identified based on visual information such as the area where the power outage occurred and whether the distribution line is sagging. In the case of a break in a branch line, no change in voltage occurs in the sensor switch installed on the main line when the break occurs, so the break cannot be detected. The introduction of a system using smart meters that can automatically and quickly detect breaks in distribution lines and identify their location is also being considered.

[0003] Typically, power is distributed using three-phase AC except in areas immediately adjacent to end-user facilities, with three electric wires installed along a single distribution route. It is extremely rare for all three electric wires to break simultaneously; typically, only one breaks. When one electric wire breaks, power is supplied downstream of the break from the remaining two electric wires, causing the voltage magnitude of the broken phase to be halved and the phase of the broken phase to shift by 180°. To detect a break based on this change, a detector that detects voltage or phase must be installed downstream of the break. Therefore, to locate a break using this method, multiple detectors must be installed. One proposed technique for estimating the break location using fewer detectors is to install current detectors on both the power supply side and the end side of a common ground wire, and estimate the break location based on the relationship between the time difference between the zero-crossing points of the two measured currents and the distance from the measurement points to the break (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2022-145081 Summary of the Invention [Problem to be solved by the invention]

[0005] Actual power distribution networks have many branch lines. The method of estimating the point of a wire break based on the time difference between the zero-crossing points of the current flowing through current measuring devices installed on the power supply side and the terminal side of a common ground wire requires measuring the current in the common ground wire downstream of the break point. However, installing equipment to measure the current in the common ground wire at the terminals of all branch lines in a power distribution network with many branch lines increases equipment costs. Therefore, an object of the present invention is to provide a wire break detection system, current state measuring device, wire break detection method, and wire break detection program that can detect wire breaks with a relatively simple configuration. [Means for solving the problem]

[0006] (1) A wire break detection system according to one embodiment of the present invention is arranged on a trunk line of a three-phase AC power distribution network including a trunk line and branch lines branching off from the trunk line, sandwiching a branch point of at least one of the branch lines, and includes a plurality of current measuring devices that measure waveforms of three-phase currents, a phase difference calculator that calculates the mutual phase differences of the three-phase currents based on the waveforms measured by the current measuring devices, and a wire break estimator that estimates that a wire break has occurred when the phase difference calculated by the phase difference calculator changes.

[0007] (2) In the above-described open circuit detection system (1), the open circuit estimator may estimate that an open circuit has occurred in the branch line between the current measuring device that measured a current for which it is determined that the phase difference has changed and the current measuring device downstream thereof that measured a current for which it is determined that the phase difference has not changed.

[0008] (3) In the open circuit detection system of (2) above, when it is determined that the phase difference has changed in all of the current measuring devices, the open circuit estimator may estimate that an open circuit has occurred further distal than the most distal current measuring device.

[0009] (4) In the disconnection detection systems described above in (1) to (3), the phase difference calculator may be provided integrally with each of the current measuring devices.

[0010] (5) Another aspect of the present invention provides a current status measuring device comprising a plurality of current measuring devices that measure the waveforms of three-phase currents, a phase difference calculator that calculates the phase differences between the three-phase currents based on the waveforms measured by the current measuring devices, and a data transmitter that transmits data on the phase differences calculated by the phase difference calculator.

[0011] (6) Another aspect of the present invention provides a method for detecting a disconnection, the method comprising the steps of: measuring waveforms of three-phase currents at a plurality of measurement points on a trunk line of a three-phase AC power distribution network including a trunk line and branch lines branching off from the trunk line, the measurement points sandwiching a branch point of at least one of the branch lines; calculating phase differences between the three-phase currents based on the measured waveforms; and estimating that a disconnection has occurred when the calculated phase difference changes.

[0012] (7) Another aspect of the present invention provides a disconnection detection program that causes a computer device to function as a disconnection determination device that estimates the occurrence of a disconnection in a three-phase AC power distribution network that includes a trunk line and branch lines branching off from the trunk line, and includes: a phase difference acquisition unit that executes a function of acquiring the mutual phase differences of the three-phase currents calculated from the waveforms of the three-phase currents measured at a plurality of measurement points on the trunk line that sandwich a branch point of at least one of the branch lines; and a disconnection estimation unit that executes a function of estimating that a disconnection has occurred when the phase difference acquired by the phase difference acquisition unit changes. [Effects of the Invention]

[0013] According to the present invention, a wire break can be detected with a relatively simple configuration. [Brief explanation of the drawings]

[0014] [Figure 1] 1 is a schematic diagram showing a three-phase AC power distribution network equipped with a wire break detection system according to an embodiment of the present invention. [Figure 2] FIG. 2 is a circuit diagram of a branch line of the three-phase AC distribution network of FIG. 1. [Figure 3] 10 is a vector diagram illustrating a change in current in a branch line due to a line break; DETAILED DESCRIPTION OF THE INVENTION

[0015] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described with reference to the drawings. Fig. 1 is a schematic diagram showing the configuration of a wire break detection system 1 according to a first embodiment of the present invention.

[0016] The wire break detection system 1 estimates the occurrence of a wire break in a three-phase AC power distribution network 100 including a trunk line 110 and branch lines 120 branching off from the trunk line 110. The wire break detection system 1 implements a wire break detection method according to the present invention. Note that the terms "trunk line" and "branch line" are relative terms, and a branch line branching off from a trunk line can be interpreted as the trunk line of the next hierarchical level, and a three-phase AC power distribution network branching off into multiple layers including further branch lines branching off from this trunk line can also be envisioned. A load L can be connected to the trunk line 110 and the branch lines 120 in a distributed manner. The wire break detection system 1 includes a plurality of current state measuring devices 10 and a wire break determination device 20.

[0017] The current state measuring device 10 itself is one embodiment of the current state measuring device according to the present invention. The current state measuring device 10 is disposed on the trunk line 110 across the branch point of at least one branch line 120. The current state measuring device 10 includes a current measuring device 11, a phase difference calculator 12, and a data transmitter 13. The current state measuring device 10 may be configured by a dedicated electronic circuit or by a computer device executing an appropriate control program. Each component of the current state measuring device 10 may be conceptualized based on its function and may not be clearly distinguishable in terms of physical configuration and program configuration. A plurality of current state measuring devices 10 may be provided in a distributed manner on the trunk line 110, each attached to a facility such as a switchyard.

[0018] The current measuring device 11 measures the waveforms of each of the three phases of current. That is, the current measuring device 11 repeatedly measures (samples) the current value of the first phase (hereinafter referred to as R phase), the current value of the second phase (hereinafter referred to as S phase), and the current value of the third phase (hereinafter referred to as T phase) of the trunk line 110 at each installation position at a frequency sufficiently higher than the frequency of the three-phase AC. To enable the phase difference calculator 12 to calculate an accurate phase, the sampling frequency of the current measuring device 11 is preferably 8 kHz or higher, and more preferably 10 kHz or higher.

[0019] The phase difference calculator 12 calculates the phase differences between the three-phase currents based on the waveforms measured by the current measuring instrument 11. That is, the phase difference calculator 12 calculates the phase difference between the R-phase current and the S-phase current of the main line 110, the phase difference between the S-phase current and the T-phase current, and the phase difference between the T-phase current and the R-phase current.

[0020] The phase difference calculator 12 may be provided in the wire breakage determination device 20, but is preferably provided integrally with each phase difference calculator 12, that is, individually in each current state measuring device 10, as in this embodiment. In order to calculate an accurate phase, it is desirable for the phase difference calculator 12 to accurately acquire the waveform of the current value, that is, to acquire current value data at a high sampling rate from the current measuring device 11. For this reason, rather than providing the phase difference calculator 12 in the wire breakage determination device 20 and enabling communication of a huge amount of data between the current state measuring device 10 and the wire breakage determination device 20, it is possible to build a cheaper and more reliable system by providing the phase difference calculator 12 individually in the current state measuring device 10, thereby reducing the amount of communication data.

[0021] The data transmitter 13 transmits the phase difference data calculated by the phase difference calculator 12 to the line-break determination device 20 through a communication line. The data transmitter 13 may also serve as a communication device provided for controlling a switch, for example. The data transmitter 13 may also transmit the phase difference data to the line-break determination device 20 via a data relay device, for example, a communication device for a switch. The communication line may be a dedicated communication line laid together with the three-phase AC power distribution network 100, or may be a public communication network, all or part of which may include wireless communication such as the Internet or telephone lines.

[0022] The line break determination device 20 has a data receiver 21, a line break estimator 22, and an alarm 23. The line break determination device 20 may be configured by a dedicated electronic circuit, but typically may be configured by one or more computers having a memory, a processor, an input / output interface, etc., and executing appropriate programs. The line break determination device 20 may be configured integrally with a computer that controls equipment in the three-phase AC distribution network 100, such as switches installed in each switching station. The line break determination device 20 and its components may be conceptualized based on their functions, and may not be clearly distinguishable in terms of physical configuration and program configuration.

[0023] The data receiver 21 receives the phase difference data from the data transmitter 13 of each current state measuring device 10. The data receiver 21 can also be used as a communication device used for controlling the three-phase AC power distribution network 100.

[0024] The wire breakage estimator 22 estimates that a wire breakage has occurred when the phase difference calculated by the phase difference calculator 12 changes. Fig. 2 shows a circuit diagram of a model of a branch line 120 to which a plurality of loads Ln (n indicates the number of the load) are connected in a distributed manner. The branch line 120 includes an R-phase electric wire W R , S-phase wire W S and T-phase wire W T Each load Ln has a partial load L RS n,L ST n,L TR n. Partial load L RS n,LST n,L TR n are the partial load currents I RS n,I ST n,I TR n flows.

[0025] In Figure 2, the S-phase wire W S If the load L2 breaks between the second load L2 and the third load L3 (the point indicated by "x"), the loads L1 to L2 upstream of the break point will have equal three-phase currents, but the loads L3 to L5 downstream of the break point will have only a partial load L between the T phase and the R phase. TR 3,L TR 4,L TR 5 only at partial load current I TR 3,I TR 4,I TR 5 plays.

[0026] FIG. 3 shows the current I of each phase at the base end of the branch line 120. R ,I S ,I T In Figure 3, the case without a break is shown by a dashed line, and the case with a break is shown by a solid line. The R-phase current I R is the partial load current I between the R and S phases RS The sum of n and the partial load current I between the T and R phases TR n, and the S-phase current I S is the partial load current I between the S and T phases ST The sum of n and the partial load current I between the R and S phases RS n, and the T-phase current I T is the partial load current I between the T and R phases TR The sum of n and the partial load current I between the S and T phases ST It is the difference from the sum of n.

[0027] If there is no break in the wire, the three partial load currents I RS n,I ST n,I TR Since the magnitudes of n are equal, each wire W R ,W S ,W T The phase of the current supplied to the load from the starting wire W R ,WS ,W T Therefore, when there is no break in the wire, the current I R ,I S , I T Phase difference θ RS ,θ ST ,θ TR is approximately equal at about 120°. Note that the load Ln may include a single-phase load, so the partial load L RS n,L ST n,L TR The imbalance in n causes the current I R ,I S , I T The phase difference may deviate slightly from 120°.

[0028] S-phase wire W S If a break occurs between the second load L2 and the third load L3, the loads L1 and L2 upstream of the break point will have equal partial load currents I with a phase difference of 120°. RS 1,I ST 1,I TR 1, I RS 2,I ST 2,I TR 2 flows, but the loads L3 to L5 downstream of the break point are subject to partial load current I TR 3,I TR 4,I TR Since only the current flows through the R-phase wire W downstream of the broken wire, R and the current flowing through the T-phase wire W T The phase difference between the currents flowing through the phase current I at the base end of the branch line 120 is 180°. R ,I S , I T is the total partial load current I TR n,I TR n,I TR Since it is the sum of n, the S-phase wire W S If the wire breaks midway, the R-phase current I R and S-phase current I S Phase difference θ RS and S-phase current I S and T-phase current I T Phase difference θ ST decreases from 120° before the disconnection, and the T-phase current I Tand R-phase current I R Phase difference θ TR increases from 120° before the break.

[0029] The current of each phase measured by current measuring instrument 11 of current state measuring device 10 installed on trunk line 110 is the sum of the currents of load L on trunk line 110 and branch line 120 downstream from the position where current state measuring device 10 is installed. Therefore, if there is a significant change in the phase difference detected by current measuring instrument 11, it can be determined that there is a break in the line downstream of current measuring instrument 11 that measured the current where it is determined that the phase difference has changed.

[0030] The disconnection estimator 22 may also be configured to estimate that a disconnection has occurred in a branch line 120 between a current measuring device 11 that measures a current determined to have changed in phase and a current measuring device 11 downstream of the current measuring device 11 that measures a current determined to have no change in phase. As described above, current flows only between two phases downstream of the disconnection point, but this current is supplied from the upstream side of the disconnection point. Conversely, even if a disconnection occurs in one of the branch lines 120, the disconnection does not affect the main line 110 downstream of the branch point of the branch line 120 or other branch lines 120. Therefore, it can be determined that a disconnection has occurred in the branch line 120 branching off from the main line 110 between the current measuring device 11 whose phase difference has changed and the current measuring device 11 downstream of the current measuring device 11 whose phase difference has not changed. The disconnection estimator 22 may also be configured to estimate that a disconnection has occurred further distal than the most distal current measuring device 11 when all current measuring devices 11 determine that the phase difference has changed.

[0031] When the line break estimator 22 estimates that a line break has occurred, the alarm 23 notifies the occurrence of the line break and the estimated location of the line break. This can prompt the manager of the three-phase AC power distribution network 100 to take measures such as establishing another power distribution route to the area where the power outage is occurring, or to arrange for work to restore the line break. The line break notification may be made to the manager directly by visual information, auditory information, or the like, or may be made by sending a signal indicating the occurrence of the line break to another device such as the manager's mobile terminal.

[0032] A wire break detection method according to one embodiment of the present invention, which is implemented in the wire break detection system 1, includes the steps of measuring the waveforms of three-phase currents at a plurality of measurement points set on the main line 110 of the three-phase AC power distribution network 100 and sandwiching a branch point of at least one branch line 120, calculating the phase differences between the three-phase currents based on the measured waveforms, and inferring that a wire break has occurred when the calculated phase difference changes.

[0033] In addition, in the disconnection detection system 1, a disconnection estimation program according to one embodiment of the present invention that causes a computer device to function as the disconnection determination device 20 includes a phase difference acquisition unit that executes the function of a data receiver 21 that acquires the mutual phase differences of three-phase currents calculated from the waveforms of the three-phase currents measured at a plurality of measurement points sandwiching the branch point of at least one branch line 120 on the main line 110, and a disconnection estimation unit that executes the function of a disconnection estimator 22 that estimates that a disconnection has occurred when the phase difference acquired by the phase difference acquisition unit changes.

[0034] As described above, the disconnection detection system 1 can detect the occurrence of a disconnection in the branch line 120 with a relatively simple equipment configuration that only detects the phase difference of the current in the main line 110.

[0035] The above describes embodiments of the disconnection detection system, current state measuring device, disconnection detection method, and disconnection detection program of the present invention, but the disconnection detection system, current state measuring device, disconnection detection method, and disconnection detection program of the present invention and their effects are not limited to those described above. [Explanation of symbols]

[0036] 1. Disconnection detection system 10 Current status measuring device 11 Current measuring device 12 Phase difference calculator 13 Data transmitter 20. Disconnection detection device 21 Data receiver 22 Breakdown estimator 23 Alarm 100 3-phase AC distribution network 110 Main line 120 Branch Line L load

Claims

1. a plurality of current measuring devices disposed on a three-phase AC power distribution network including a trunk line and branch lines branching off from the trunk line, the current measuring devices being arranged across a branch point of at least one of the branch lines, and measuring waveforms of currents of the three phases, respectively; a phase difference calculator that calculates a phase difference between the three phase currents based on the waveforms measured by the current measuring device; a disconnection estimator that estimates that a disconnection has occurred when the phase difference calculated by the phase difference calculator has changed; A wire break detection system comprising:

2. 2. The open circuit detection system of claim 1, wherein the open circuit estimator estimates that an open circuit has occurred in the branch line between the current measuring device that measured a current for which it is determined that the phase difference has changed and the current measuring device downstream thereof that measured a current for which it is determined that the phase difference has not changed.

3. The open circuit detection system of claim 2, wherein the open circuit estimator estimates that an open circuit has occurred further distal than the most distal current measuring device when it is determined that the phase difference has changed in all of the current measuring devices.

4. 4. The disconnection detection system according to claim 1, wherein the phase difference calculator is provided integrally with each of the current measuring devices.

5. a plurality of current measuring devices for measuring the waveforms of the three-phase currents; a phase difference calculator that calculates a phase difference between the three phase currents based on the waveforms measured by the current measuring device; a data transmitter that transmits data of the phase difference calculated by the phase difference calculator; A current state measuring device comprising:

6. a step of measuring waveforms of three-phase currents at a plurality of measurement points set on a three-phase AC power distribution network including a trunk line and branch lines branching off from the trunk line, the measurement points sandwiching a branch point of at least one of the branch lines; calculating a phase difference between the three phase currents based on the measured waveforms; a step of estimating that a disconnection has occurred when the calculated phase difference has changed; A disconnection detection method comprising:

7. A program that causes a computer device to function as a disconnection determination device that estimates the occurrence of a disconnection in a three-phase AC power distribution network that includes a trunk line and branch lines branching from the trunk line, the program comprising: a phase difference acquiring unit that executes a function of acquiring a phase difference between three-phase currents calculated from waveforms of the three-phase currents measured at a plurality of measurement points on the trunk line that sandwich at least one branch point of the branch line; a disconnection estimation unit that executes a function of estimating that a disconnection has occurred when the phase difference acquired by the phase difference acquisition unit changes; A disconnection detection program comprising:

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