Earth fault location estimation device and system

Abstract

To provide a device capable of precisely estimating a ground fault point by consolidating signals from the power receiving units at existing electricity consumers.SOLUTION: A ground fault point estimation device 5 includes: an estimated zero-phase component distribution database 7 that stores an estimated zero-phase component distribution which is a distribution of zero-phase components of a current or a voltage estimated when detected at multiple high-voltage consumers 10 when a ground fault occurs at any location in the distribution system 100; and an estimation unit 6 that generates a detected zero-phase component distribution that is the distribution of zero-phase components detected at multiple high-voltage consumers 10 when a ground fault occurs and estimates the location of the ground fault by comparing the detected zero-phase component distribution with the estimated zero-phase component distribution database 7.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to an apparatus and system for estimating a ground fault point in an electric power system, particularly a ground fault location in a high-voltage power distribution system. [Background technology]

[0002] Conventional methods for detecting the location of a ground fault in a high-voltage distribution system involve detecting zero-phase current with a zero-phase current transformer installed at the feeder end of a distribution substation, and detecting the presence or absence of a ground fault on a distribution line basis. In addition, the zero-phase current value and zero-phase current frequency change depending on the impedance of the distribution line, so the distance to the location where the ground fault occurred is estimated. However, these methods have a large fluctuation in the information obtained for estimation, and the accuracy is low.

[0003] A monitoring method for improving this is described, for example, in Patent Document 1. In Patent Document 1, a master station installed in a high-voltage distribution system sends a synchronous pulse signal to multiple slave stations to create a reference phase, and this reference phase is compared with the phase of the zero-phase sequence current detected at each slave station to determine the direction of the ground fault, thereby narrowing down the location where the ground fault has occurred with high accuracy. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 6-78453 Summary of the Invention [Problem to be solved by the invention]

[0005] To achieve high accuracy with the method described in Patent Document 1, it is necessary to provide a large number of master stations that transmit synchronous pulse signals to a high-voltage distribution system and slave stations that detect zero-phase currents. In addition, to improve the accuracy of earth fault location detection, it is necessary to increase the number of slave stations, which results in high costs.

[0006] Therefore, an object of the present invention is to provide a system that does not require the addition of a master station or slave station and can estimate the location of a ground fault with high accuracy by aggregating signals from the power receiving equipment of existing power consumers. [Means for solving the problem]

[0007] In order to solve the above problems, the earth fault point estimation device of the present invention has an estimated zero-sequence component distribution database that stores an estimated zero-sequence component distribution, which is the distribution of the zero-sequence components of current or voltage estimated to be detected in multiple high-voltage consumers when an earth fault occurs at any position in a distribution system, and an estimation unit that generates a detected zero-sequence component distribution, which is the distribution of the zero-sequence components detected in multiple high-voltage consumers when an earth fault occurs, and estimates the position of the earth fault by comparing the detected zero-sequence component distribution with the estimated zero-sequence component distribution database. Effect of the Invention

[0008] According to the present invention, by aggregating signals transmitted by power receiving equipment of existing high-voltage consumers, it becomes possible to estimate with high accuracy the location of a ground fault occurring in a high-voltage distribution system without adding a parent station or child station to the high-voltage distribution system. Further features related to the present invention will become apparent from the description of the present specification and the accompanying drawings. Furthermore, the problems, configurations and effects other than those described above will become apparent from the following description of the embodiments. [Brief description of the drawings]

[0009] [Figure 1] 1 is a diagram showing a high-voltage power distribution system to which a ground fault detection device according to the present invention is applied; [Diagram 2] 4 is a diagram showing the relationship between the position where a ground fault occurs and the waveforms of the zero-phase sequence voltage and the zero-phase sequence current detected in the power receiving equipment of a high-voltage consumer. [Diagram 3] Zero-phase current peak value distribution for high-voltage customers. [Figure 4] 4 is a flowchart showing a process executed by the ground fault point estimating device according to the first embodiment. [Diagram 5] 10 is a flowchart showing a process executed by a ground fault point estimating device according to a second embodiment. [Figure 6] Another example of a connection diagram of a high-voltage customer's power receiving equipment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] Preferred embodiments of the present invention will be described below with reference to the drawings. Note that the following are merely examples of the present invention, and the contents of the present invention are not limited to the specific embodiments described below. The present invention can of course be modified into various embodiments, including the embodiments described below.

[0011] [Example 1] A first embodiment will be described with reference to Fig. 1 to Fig. 4. Fig. 1 is a diagram of a high-voltage distribution system to which a ground fault point estimating device 5 according to the first embodiment is applied. A high-voltage distribution system 100 has a distribution substation 1, high-voltage consumers 10a, 10b, and 10c, a ground fault point estimating device 5, and a high-voltage distribution line 8 that connects the distribution substation 1 with the high-voltage consumers 10a, 10b, and 10c. The distribution substation 1 includes a zero-phase current transformer 2, a grounded instrument transformer 3, and a transmission transformer 4 as power sending-out facilities.

[0012] The high voltage consumer 10a includes a zero-phase current transformer 2a, a capacitor-type earth fault detector 11a, a signal sending unit 12a, a power receiving transformer 13a, a switch protection device 14a, and a power receiving control device 15a as power receiving equipment. The zero-phase current transformer 2a measures the zero-phase current, i.e., the zero-phase component of the current, and the capacitor-type earth fault detector 11a measures the zero-phase voltage, i.e., the zero-phase component of the voltage. The signal sending unit 12a transmits a signal detected by the power receiving equipment of the high voltage consumer 10a to the ground fault point estimation system 5 via the information transmission line 9. The switch protection device 14a protects the transformer and distribution line within the premises when a fault such as a short circuit or a ground fault occurs in the high voltage consumer 10a. The power receiving control device 15a controls the power receiving state of the high voltage consumer 10a. The signal sending unit 12a also receives time information from, for example, a GPS 20 in order to time stamp the zero-phase component signal to be transmitted. The high voltage customers 10b and 10c are each configured in a similar manner. Note that the number of high voltage customers is not limited to that shown in FIG.

[0013] The earth fault point estimating device 5 also has an estimating unit 6 that estimates the position of an earth fault that has occurred in the high-voltage distribution system 100, and an estimated zero-phase-sequence component distribution database 7 that stores information on the estimated zero-phase-sequence component distribution described later. A method by which the earth fault point estimating device 5 estimates the position of an earth fault will be described later in detail. The earth fault point estimating device 5 is installed, for example, as a computer equipped with a CPU and a memory, in a central load dispatching center that controls the power distribution status of multiple distribution substations.

[0014] When a line-to-ground fault occurs in the high-voltage distribution system 100, a zero-phase current I flows from the distribution substation 1 and the high-voltage consumers 10a, 10b, and 10c toward the point where the line-to-ground fault occurs. 00 , I 0a , I 0b , I 0c At the same time, the zero-phase voltage V 0a , V 0b , V 0c 1 shows examples in which a single-line-to-ground fault occurs at a position 30 between a distribution point 40, where a distribution line branches off to distribute power from a distribution substation 1 to a plurality of high-voltage consumers, and a high-voltage consumer 10a, a position 31 between the distribution point 40 and the distribution substation 1, and a position 32 between the distribution point 40 and a high-voltage consumer 10b.

[0015] The zero-phase current I is transmitted from the signal transmitting units 12a, 12b, and 12c of the high-voltage consumers 10a, 10b, and 10c to the earth fault point estimating device 5. 0a , I 0b , I 0c and zero-phase voltage V 0a , V 0b , V 0c A signal is sent containing information about:

[0016] FIG. 2 shows the position where a single-line ground fault occurs in the high-voltage power distribution system 100, and the zero-phase current I 0a When a line-to-ground fault 30 occurs, the zero-phase voltage V measured by the capacitor-type ground fault detector 11a of the high-voltage consumer 10a is 0a1 is a graph showing the relationship between the waveform of the zero-phase current I and the impedance of the zero-phase circuit configured in the high-voltage power distribution system 100. 0a and zero-phase voltage V 0a changes.

[0017] In Fig. 2, the ground fault location 1 is the ground fault location 31 between the distribution substation 1 and the distribution point 40 in Fig. 1, the ground fault location 2 is the ground fault location 30 shown in Fig. 1, and the ground fault location 3 is the ground fault location 32 shown in Fig. 1. The change in the ground fault location is particularly noticeable in the zero-phase current I 0a It can be seen that the peak value of the zero-phase current / zero-phase voltage changes. By analyzing the obtained data by various methods, it is also possible to analyze changes in the peak value, frequency, damping time constant of the high-frequency component, or the ratio of the maximum value for each ground fault location. Similar data can be obtained for the high-voltage consumers 10b and 10c. In this specification, the peak value, frequency, damping time constant of the high-frequency component, or the ratio of the maximum value of the zero-phase current / zero-phase voltage are collectively referred to as the zero-phase component, and the signal including information about the zero-phase component sent from the signal sending unit 12 to the ground fault point estimation device 5 is referred to as the zero-phase component signal.

[0018] FIG. 3 is a distribution diagram showing the peak values ​​of the zero-phase currents among the above-mentioned zero-phase components. For example, when a single-line ground fault occurs at a ground fault position 1, the zero-phase current I 0a-1 , I 0b-1 , I 0c-1 If the peak values ​​of the zero-phase current of a high-voltage consumer are plotted, the distribution is 21-1, indicated by the symbol ◇ in FIG. 3. Similarly, the distributions of the peak values ​​of the zero-phase current of a high-voltage consumer when a single-line ground fault occurs at ground fault locations 2 and 3 are 21-2 and 21-3, respectively. For example, the peak values ​​detected at high-voltage consumer 10a are 0a-2 , I 0a-1 , I 0a-3In other words, it can be seen that the zero-phase current detected at the high-voltage consumer 10a decreases as the location of the ground fault changes from the ground fault location 30 in Fig. 1 to the ground fault location 31 between the distribution substation 1 and the distribution point 40, and then to the ground fault location 32 between the distribution point 40 and another high-voltage consumer 10b. 0a-1 , I 0a-2 , and I 0a-3 3. The speed at which the zero-phase current is sampled by the zero-phase current transformer 2a is, for example, about 1 / 10 of the period of the zero-phase current. Furthermore, Fig. 3 also shows that the scale (output) of the power receiving equipment of the high-voltage consumer 10a and the high-voltage consumer 10c is approximately the same, and the scale of the high-voltage consumer 10b is significantly larger than those of the high-voltage consumer 10a and the high-voltage consumer 10c.

[0019] In this way, the distribution of peak values ​​of the zero-phase current I0 detected at high-voltage consumers changes depending on the location of the earth fault. In a high-voltage distribution system, information such as the resistance of substations, each high-voltage consumer, and the distribution lines connecting them is known, and the distribution of the zero-phase component estimated to be sent from each high-voltage consumer when an earth fault occurs at any position on the distribution line can be obtained by calculations using line constants. Therefore, by storing this distribution in advance as a database and comparing it with the distribution of the zero-phase component measured at a high-voltage consumer at a certain time cross section, the location of an earth fault that has occurred in the distribution system at a certain time cross section can be estimated. Note that while only high-voltage consumers are shown in Figure 3, the zero-phase current I detected at distribution substation 1 can also be calculated using the line constants. 00 The peak value of the signal may be added.

[0020] 4 is a flowchart showing a method for estimating the location of a ground fault in this embodiment. When a ground fault occurs at any location in the high-voltage distribution system 100 in step S401, a zero-phase-sequence current flows toward a ground fault point in the high-voltage distribution system 100, using the premises cable of each high-voltage consumer as a power source. A zero-phase-sequence current transformer constituting the power receiving equipment of the high-voltage consumer detects the zero-phase-sequence current, and a capacitor-type ground fault detector detects the zero-phase-sequence voltage. Based on the phase difference between the zero-phase-sequence current and the zero-phase-sequence voltage, it is determined whether the ground fault has occurred inside or outside the premises, that is, whether the ground fault has occurred inside the power receiving equipment of the high-voltage consumer or inside the high-voltage distribution system (step S402). Specifically, if the phase of the zero-phase-sequence voltage lags behind the zero-phase-sequence current, it is determined that the ground fault has occurred inside the premises, and conversely, if the phase of the zero-phase-sequence current lags behind the zero-phase-sequence voltage, it is determined that the ground fault has occurred outside the premises.

[0021] If a ground fault occurs within the facility, and if the magnitude and duration of the zero-phase current exceed the preset protection level, the system executes a protective operation within the facility, i.e., operates a circuit breaker. If the magnitude and duration of the zero-phase current do not exceed the preset protection level, the system waits without taking any action (steps S403 and S404).

[0022] When a ground fault occurs outside the premises, the signal sending unit 12 of each high voltage consumer creates information combining the zero-sequence components of the zero-sequence current I0 / zero-sequence voltage V0 with a timestamp of the time when the zero-sequence current I0 / zero-sequence voltage V0 was detected, and transmits the information to the ground fault point estimation device 5 (step S405). This timestamp is generated based on time information obtained from the GPS 20 and recorded at intervals of about 500 ns to 1 μs, for example.

[0023] The earth fault point estimation device 5 collects information from each high voltage consumer combining the above-mentioned zero-sequence components with timestamps of the times when the zero-sequence current I0 / zero-sequence voltage V0 were detected, and creates a zero-sequence component distribution for each high voltage consumer for each timestamp, such as the zero-sequence current peak value distribution shown in Figure 3 (steps S407, 408).

[0024] Furthermore, prior to the above-mentioned flow, the earth fault point estimation device 5 pre-calculates the zero-phase component distribution of high-voltage consumers for each earth fault location from the impedance map of the high-voltage distribution system 100, and creates an estimated zero-phase component distribution database 7 shown in Figure 1 (step S406).

[0025] Then, the estimation unit 6 of the ground fault point estimation device 5 compares the detected zero-phase-sequence component distribution of the high-voltage consumer 10 for each time stamp sent from the signal sending unit 12 with the estimated zero-phase-sequence component distribution database 7, and extracts any matching estimated zero-phase-sequence component distribution (step S409). Whether or not there is a matching distribution is determined by evaluating the similarity according to a preset index (step S409). As an index for evaluating the similarity, a correlation coefficient or Euclidean distance between distributions is used.

[0026] When an estimated zero-phase-sequence component distribution that matches the detected zero-phase-sequence component distribution is extracted, it is determined that the location of the earth fault corresponding to the detected zero-phase-sequence component distribution matches the location of the earth fault corresponding to the matched estimated zero-phase-sequence component distribution, and the time stamp and earth fault location information are combined and sent to the data collection unit, the isolated operation planning unit, and the restoration decision-making support unit (step S410). If a matching estimated zero-phase-sequence component distribution is not extracted, the system remains on standby. The above flow makes it possible to estimate the location of the earth fault, but as shown in step S411, the above data may be accumulated and the estimated zero-phase-sequence component distribution database 7 may be updated.

[0027] As described above, in this embodiment, the detected zero-phase-sequence component distribution created based on the zero-phase-sequence components detected at each high-voltage consumer when a ground fault occurs is compared with a pre-created estimated zero-phase-sequence component distribution database, making it possible to estimate the location of a ground fault with high accuracy. Moreover, this method uses only the power receiving equipment that each high-voltage consumer originally has, and does not require the installation of additional equipment, making it extremely advantageous in terms of cost.

[0028] Even if it is not possible to collect information combining zero-phase components and time stamps from all high-voltage customers, it is possible to estimate the location of a ground fault from information collected from some of the high-voltage customers.

[0029] [Example 2] A second embodiment of the present invention will be described with reference to Fig. 5. In the second embodiment, the earth fault point estimating device 5 has the same configuration as that of the first embodiment, but when the configuration including the earth fault point estimating device 5 and the group of high voltage consumers 10 connected to the device via an information transmission line 9 is regarded as an earth fault point estimating system, the flow executed in the system is different from that of the first embodiment. In the second embodiment, step S501 is additionally executed in which information combining the zero-phase sequence component and the time stamp generated in step S405 of Fig. 4 is transmitted to the earth fault point estimating device 5 by a batch transmission method in which the information is transmitted at a predetermined time.

[0030] In this embodiment, in addition to the same effects as those of the first embodiment, an effect of leveling the traffic on the transmission path by using the batch transmission method can be obtained.

[0031] [Other configurations of high voltage customers] In the above embodiment, the power receiving equipment of the high voltage consumer 10a is configured to branch and supply the signal of the zero-phase current transformer 2a to the signal sending unit 12a and the power receiving control device 15a, but it can also be configured as shown in FIG. 6. The power receiving equipment of the high voltage consumer 10a shown in FIG. 6 once supplies the signal of the zero-phase current transformer 2a in the high voltage consumer 10a to the power receiving control device 15a, and transfers the zero-phase current signal from the power receiving control device 15a to the signal sending unit 12a. In the configuration shown in FIG. 1, it is possible to apply the present invention without adding any equipment to the high voltage consumer side, and it is possible to reduce the equipment introduction cost. However, even by adopting the configuration shown in FIG. 6, the existing switching protection system consisting of the zero-phase current transformer 2a, the power receiving control device 15a, and the switching protection device 14a can be preserved as it is, and the signal sending unit 12a can be added later, so there is no risk of impairing the reliability of the existing switching protection system. The same applies to the power receiving equipment of other high voltage consumers.

[0032] According to the embodiment of the present invention described above, the following advantageous effects are obtained. (1) The earth fault point estimation device of the present invention, which estimates the location of an earth fault occurring in a distribution system that supplies power to a plurality of high-voltage consumers, has an estimated zero-sequence component distribution database that stores an estimated zero-sequence component distribution, which is the distribution of the zero-sequence component of the current or voltage estimated to be detected in a plurality of high-voltage consumers when an earth fault occurs at any position in the distribution system, and an estimation unit that generates a detected zero-sequence component distribution, which is the distribution of the zero-sequence component detected in the plurality of high-voltage consumers when an earth fault occurs, and estimates the location of the earth fault by comparing the detected zero-sequence component distribution with the estimated zero-sequence component distribution database.

[0033] With the above configuration, by aggregating signals transmitted by the power receiving equipment of existing high-voltage customers, it becomes possible to estimate with high accuracy the location of a ground fault that has occurred in the high-voltage distribution system without adding a parent station or child station to the high-voltage distribution system.

[0034] (2) The zero-phase component is the ratio of the peak value, frequency, or damping time constant of the high-frequency component of the zero-phase current or voltage, or the maximum value. This makes it possible to generate multiple detection zero-phase distributions, thereby improving the accuracy of estimating the ground fault point.

[0035] (3) The estimation unit evaluates the detected zero-phase component distribution and the estimated zero-phase component distribution based on the correlation coefficient or Euclidean distance between the distributions. In the present invention, since the generation of the estimated zero-phase component distribution and the detected zero-phase component distribution does not require complicated calculation processing, the similarity between the distributions can be evaluated by the above-mentioned simple method.

[0036] (4) The estimation unit generates a detected zero-phase component distribution based on the time information when the zero-phase component was detected. Since the distance from the signal sending unit to the earth fault point estimation device differs for each high-voltage consumer, there is also a difference in the time from when an earth fault occurs until the zero-phase component signal is transmitted to the earth fault point estimation device. Therefore, if multiple earth faults occur within a short period of time due to multiple lightning strikes, etc., there is a risk that the zero-phase component signals will be mixed and it will be impossible to accurately generate a detected zero-phase component distribution. However, the above configuration makes it possible to ignore the difference in transmission path distance, making it possible to accurately generate a detected zero-phase component distribution.

[0037] (5) A system for estimating an earth fault point including the earth fault point estimating device according to (1) and a plurality of high voltage consumers connected to the device via an information transmission line, in which the high voltage consumers transmit information combining a zero-phase component and time information when the zero-phase component was detected to the earth fault point estimating device via the information transmission line in a batch manner at predetermined time intervals. This allows the transmission traffic to be leveled out, realizing more stable information transmission than when information is transmitted every time a ground fault occurs.

[0038] (6) A system for estimating a ground fault point including the ground fault point estimating device described in (1) and a plurality of high-voltage consumers connected to the device via an information transmission line, in which a zero-phase current signal detected by a zero-phase current transformer provided in the power receiving equipment of the high-voltage consumer is input to both a signal sending unit and a power receiving control device provided in the power receiving equipment. This makes it possible to apply the present invention without adding any equipment to the high-voltage consumer side, thereby reducing the cost of introducing the equipment.

[0039] (7) A system for estimating a ground fault point including the ground fault point estimating device described in (1) and a plurality of high-voltage consumers connected to the device via an information transmission line, in which a zero-phase current signal measured by a zero-phase current transformer provided in the power receiving equipment of the high-voltage consumer is input to a power receiving control device provided in the power receiving equipment and is further transferred from the power receiving control device to a signal sending unit provided in the power receiving equipment. This allows the existing switching protection system consisting of the zero-phase current transformer, the power receiving control device, and the switching protection device to be preserved as is, and the signal sending unit can be added later, so there is no risk of compromising the reliability of the existing switching protection system.

[0040] The present invention is not limited to the above-described embodiments, and various modifications are possible. For example, the above-described embodiments have been described in detail to clearly explain the present invention, and the present invention is not necessarily limited to an embodiment having all of the configurations described. It is also possible to replace a part of the configuration of one embodiment with the configuration of another embodiment. It is also possible to add the configuration of another embodiment to the configuration of one embodiment. It is also possible to delete a part of the configuration of each embodiment, or to add or replace another configuration. [Explanation of symbols]

[0041] 2a, 2b, 2c zero-phase current transformer, 5 earth fault point estimating device, 7 estimated zero-phase component distribution database, 9 information transmission line, 10a, 10b, 10c high voltage consumer, 12a, 12b, 12c signal sending unit, 15a, 15b, 15c power receiving control device

Claims

1. A ground fault point estimation device that estimates a position of a ground fault occurring in a power distribution system that supplies power to a plurality of high-voltage consumers, an estimated zero-sequence component distribution database that stores an estimated zero-sequence component distribution, which is a distribution of zero-sequence components of a current or a voltage estimated to be detected in the plurality of high voltage consumers when the ground fault occurs at an arbitrary position in the power distribution system; an estimation unit that generates a detected zero-phase component distribution, which is a distribution of the zero-phase components detected in the plurality of high voltage consumers, when the ground fault occurs, and estimates a position of the ground fault by comparing the detected zero-phase component distribution with the estimated zero-phase component distribution database. A ground fault point estimating device characterized by the above.

2. 2. The ground fault point estimating device according to claim 1, wherein the zero-phase component is a peak value of a zero-phase current or a zero-phase voltage. A ground fault point estimating device characterized by the above.

3. 2. The ground fault point estimating device according to claim 1, wherein the zero-phase component is a frequency of a zero-phase current or a zero-phase voltage. A ground fault point estimating device characterized by the above.

4. 2. The ground fault point estimating device according to claim 1, wherein the zero-phase component is a damping time constant or a maximum value ratio of a high-frequency component of a zero-phase current or a zero-phase voltage. A ground fault point estimating device characterized by the above.

5. 2. The ground fault point estimating device according to claim 1, wherein the estimating unit evaluates the detected zero-phase component distribution and the estimated zero-phase component distribution based on a correlation coefficient or a Euclidean distance between the distributions. A ground fault point estimating device characterized by the above.

6. 2. The ground fault point estimating device according to claim 1, wherein the estimating unit generates the detected zero-phase component distribution based on time information when the zero-phase component is detected. A ground fault point estimating device characterized by the above.

7. 2. An earth fault point estimation system including the earth fault point estimation device according to claim 1 and a plurality of high voltage consumers connected to the device via an information transmission line, wherein the high voltage consumers transmit information combining the zero-phase component and time information when the zero-phase component was detected to the earth fault point estimation device via the information transmission line in a batch manner at predetermined time intervals. A ground fault location estimation system comprising:

8. 2. A ground fault point estimation system including the ground fault point estimation device according to claim 1 and a plurality of high voltage consumers connected to the device via an information transmission line, wherein a zero-phase-sequence current signal detected by a zero-phase-sequence current transformer provided in a power receiving facility of the high voltage consumer is input to both a signal sending unit and a power receiving control device provided in the power receiving facility, A ground fault location estimation system comprising:

9. 2. A ground fault point estimation system including the ground fault point estimation device according to claim 1 and a plurality of high voltage consumers connected to the device via an information transmission line, wherein a zero-phase-sequence current signal measured by a zero-phase-sequence current transformer provided in a power receiving facility of the high voltage consumer is input to a power receiving control device provided in the power receiving facility, and is further transferred from the power receiving control device to a signal sending unit provided in the power receiving facility. A ground fault location estimation system comprising:

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