JP3236186U - Selection of zero-phase current flowing through the ground wire of a single-phase high-voltage cable - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a high-voltage cable failure detection device having a function of selecting a ground fault current and a charging current, improving detection ability and suppressing unnecessary operation. A high-voltage cable failure detection device detects a phase difference between currents in the case of a cable that can detect two zero-phase currents when the high-voltage cable has a ground fault. In that case, the criterion for determining the ground fault current is that if the large current advances within 150 ° to 180 °, the large current is determined to be the ground fault current, and in other cases, it is determined to be the charging current. A reference value is set for a cable that may not be able to detect two currents, and if a current exceeding the reference value is detected in the target cable, it is determined as a ground fault current. If two currents are detected, priority is given to detecting the phase difference and selecting based on the determination criteria. Combining the determination means with a cable in this way helps to improve the detection capability and suppress unnecessary operations. [Selection diagram] Fig. 1

Description

The present invention is a detector that displays the phase of a ground-faulted high-pressure cable by selecting whether the 0-phase current flowing through the ground wire of the single-phase high-pressure cable is a ground fault current or a charging current and reacting only with the ground fault current. Hereinafter, it is referred to as a “detector”).

When the high-voltage cable has a ground fault, a ground fault current corresponding to the ground capacitance and ground fault resistance of the electric circuit flows through the ground wire of the high-voltage cable. Also, if a ground fault occurs in a place other than the high-voltage cable (hereinafter referred to as "another place") while the high-voltage cable is in a healthy state, it depends on the 0-phase voltage generated at that time and the capacitance of the high-voltage cable. The charging current flows through the ground wire of the high voltage cable. (Hereinafter, when both the ground fault current and the charging current are shown in the present invention, they are referred to as "zero-phase current".)

When a high-voltage cable has a ground fault or a ground fault occurs elsewhere, there are many cases of transition to arc discharge. Then, when the arc discharge is reached, the zero-phase current increases due to the generation of harmonics, and in a remarkable case, it may increase three times or more.

The detector must reliably detect and operate the ground fault current in the event of a ground fault in the high voltage cable, but must not operate in the charging current detected by the high voltage cable in a healthy state. However, the selection between the two that has been performed so far has been a method of distinguishing by the magnitude of the current. Therefore, the operating current value of the detector is set to a value higher than the maximum charging current of the high-voltage cable to which the detector is attached by further triple.

Japanese Unexamined Patent Publication No. 11-306440 Japanese Unexamined Patent Publication No. 2001-31409

"High Voltage Cable Failure Detector Product Information", Sanki Seisakusho Co., Ltd., 2021, Home Page (https://www.sanks.co.jp/company)

Until now, it was assumed that the ground fault of the high-voltage cable would lead to a complete ground fault, but it was found that there were cases where the ground fault remained at a high resistance ground fault. In such a case, the value of the ground fault current becomes smaller than the set value of the detector, so even if the high voltage circuit breaker on the power supply side (hereinafter referred to as "high voltage circuit breaker") cuts off, the detector will still have the ground fault current. Cannot be detected.

If the high-voltage circuit breaker shuts off, search for the accident point immediately. However, if the detector attached to the high-voltage cable with a ground fault does not indicate the failure of the high-voltage cable, it is judged that there is no abnormality in the cable and the subsequent search is continued. If all the visual searches are completed and the insulation defective part cannot be found, the dielectric strength test for each section is sequentially performed as the next search means. By repeating the dielectric strength test, it is possible to reach the location of the cable that has a ground fault, but the non-display of the detector guides the accident search in an unrelated direction, which wastes the time and effort required for the search. There were drawbacks.

In order to make up for the shortcoming, if the detector is equipped with a function of selecting the ground fault current and the charging current, the ground fault current can be operated accurately and the charging current can be suppressed from operating. By doing so, the detector operating current value can be set to the same value as the setting value of the ground fault protection device on the power supply side, and if the high voltage circuit breaker shuts off due to the high resistance ground fault of the high voltage cable, the detector will also be set. By always working, it tries to solve the above-mentioned drawbacks.

The present invention applies the characteristics of the ground fault current and the charging current in a single-phase high-voltage distribution line to select both. First, the basic concept will be described with reference to FIGS. 2 to 5. The phase expression in the present invention is A phase or B phase, and the ground fault phase is specifically described as A phase.

When a high-voltage cable has a ground fault in a single-phase 6.6 kV high-voltage distribution line, a ground fault current Ig (hereinafter referred to as "Ig") and a charging current Ica (hereinafter referred to as "Ica") are applied to the grounding wire of phase A. Flows. As shown in FIG. 2, Ig leads the phase voltage Ea of the A phase and becomes a current. Further, the size is from several hundred mA to several A. As shown in FIG. 3, Ica has a lead of 90 ° with respect to the ground voltage Ega of the A phase. The size is determined by Ega and the capacitance Cx of the cable (hereinafter referred to as "Cx"). Since Ega varies from 0V to 3,300V, Ica is as small as 0 to several hundred mA. In addition, Ig and Ica are synthesized and detected. The combined current is referred to as Iga below. The magnitude and phase of the combined current Iga are not so different from the magnitude of Ig as shown in FIG. 4, but the phase is slightly ahead of Ig.

The charging current Icb (hereinafter referred to as “Icb”) flowing through the ground wire of the B phase is 90 ° ahead of the ground voltage Egb of the B phase as shown in FIG. Further, the voltage to ground Egb lags behind the phase B phase voltage Eb in the range of 0 ° to a maximum of 19.5 ° as shown in FIG. Therefore, the phase of the Icb changes in a limited range of 0 ° to 19.5 ° with respect to the Y axis as shown in FIG. The size of Icb is determined by the size of Egb and Cx. Egb approaches 3,300V from a maximum of 6,600V due to increased ground fault resistance. Therefore, the size of Icb varies greatly from several tens of mA to about 1 A depending on the size of Cx.

The current flowing through the A-phase grounding wire during a ground fault of the high-voltage cable is Iga, and the current flowing through the B-phase grounding wire is Icb. Further, the current flowing through the ground wire of the A phase at the time of a ground fault at another location is Ica, and the current flowing through the ground wire of the B phase is Icb. The sorting means for Iga and Icb in the present invention is a combination of the two sorting methods. One method is to determine the phase difference of the zero-phase current. Iga at the time of cable ground fault is larger than Icb and travels in the range of 150 ° to 180 ° than Icb. In addition, the Icb at the time of a ground fault at another location is larger than that of Ica, but the range of travel beyond Ica is limited to 90 ° to 120 °. Therefore, sorting is possible by applying this difference. However, the determination of the phase difference needs to detect Iga and Icb or Ica and Icb. Iga can be detected even if Cx is extremely small, but Icb may not be detected if Cx is small. Further, Ica cannot be detected because the voltage to ground of the A phase may be 0. Therefore, as the second selection method, when the phase difference cannot be detected, a reference value is set, and if the 0-phase current exceeds the reference value, the current is selected as Iga, and the other 0-phases are selected. We devised a method to sort the current as the charging current.

The reference value is set for cables that may detect only one 0-phase current at the time of cable ground fault, and if the detected current exceeds that value, that current is judged as the ground fault current. It is a hurdle to do. That is, the Iga at the time of a cable ground fault decreases as the ground fault resistance increases, but even at the ground fault resistance value that generates the 0-phase voltage detected by 64D, it flows by several hundred mA or more. Further, the size of Iga tends to be slightly smaller as the Cx of the cable becomes smaller, but it is almost the same if the ground fault resistance is the same. Therefore, if a value that minimizes Iga is calculated and a hurdle slightly lower than that value is provided, it is possible to determine a current equal to or greater than that hurdle as a ground fault current. This sorting method will be described with reference to FIGS. 6 to 13.

First, in the present invention, the minimum detection current that can be detected by the 0-phase current transformer is assumed to be 200 mA, and the 0-phase current that does not reach that level cannot be detected. Further, it is assumed that there are various ways to set the ground fault protection device 64D on the substation side, but in the present invention, it is premised that the high voltage circuit breaker shuts off when the detection of the 0-phase voltage by 64D reaches 80%. The capacitance of the electric circuit in the present invention is about 0.5 μF to 3 μF.

The ground fault resistance value at which the detection of the 0-phase voltage by 64D reaches 80% is 2,389Ω when the capacitance of the electric circuit is 0.5 μF. The Cx of the cable subject to the reference value was obtained for a cable having a ground fault resistance of 2,389 Ω and having an Icb of 200 mA or more, and a cable having a ground fault resistance of 0.12 μF or less was targeted. The reference value in this case is 800 mA. If the phase difference cannot be detected in a cable that is not subject to the reference value and exceeds this reference value, it is determined as the charging current. Further, although it is assumed that there are various values in which the Cx of the cable becomes the minimum, 0.00075μF is set assuming that the CVD 14 mm ² is about 5 m.

FIG. 6 shows the current vector and the phase difference in the case of a cable ground fault with an electric circuit capacitance of 0.5 μF (for one phase), Cx0.12 μF, and a ground fault resistance of 200 Ω. Iga is 1.03A and Icb is 0.25A, and it is possible to detect the phase difference. The detected phase difference is 179 °, which is in the range of 150 ° to 180 ° of the criterion. This cable is a reference value target cable, but if the phase difference can be detected, priority is given to the determination of the phase difference on the logic circuit. The phase of the vector shown in the figure is displayed according to the numerical value, but the magnitude is not adapted to the numerical value.

FIG. 7 is a diagram showing the current vector and the phase difference when a cable having an electric circuit capacitance of 0.5 μF and a minimum Cx of 0.00075 μF is grounded with a ground fault resistance of 200 Ω. Iga is 1.03A and Icb is 0.002A, and it is impossible to detect the phase difference. However, since Cx is 0.12 μF or less, it is a cable subject to the reference value, and Iga is 800 mA or more. Therefore, since it meets the judgment criteria, it is judged to be a ground fault current.

FIG. 8 is a diagram showing the current vector and the phase difference in the case of a ground fault with a capacitance of 0.5 μF, Cx0.12 μF, and a ground fault resistance of 2,389 Ω in the electric circuit. In this case, Iga is 0.83A, Icb is 0.21A, and the phase difference is detected at 165 °, which is within the range of the ground fault determination standard. The ground fault resistance of 2,389Ω is the ground fault resistance value when the 0-phase voltage is generated at 80%.

FIG. 9 is a diagram showing the current vector and the phase difference when a ground fault occurs with a capacitance of 0.5 μF of the electric circuit, a minimum Cx of 0.00075 μF, and a ground fault resistance of 2,389 Ω. In this case, Iga is 0.83A and Icb is 0.001A, and the phase difference cannot be detected. However, since the cable is subject to the reference value and a current of 800 mA or more is detected, the determination is a ground fault current.

FIG. 10 is a diagram showing the current vector and the phase difference in the case of a ground fault with a capacitance of 1.5 μF, Cx0.4 μF, and a ground fault resistance of 200 Ω in the electric circuit. This cable is out of the standard value. In this case, Iga is 3.06A and Icb is 0.82A. The detection of the phase difference is within the range of the ground fault criterion at 176 °.

FIG. 11 is a diagram showing the current vector and the phase difference flowing in the ground line when the same cable has a ground fault at another location. In this case, Icb is 0.82A and Ica is 0.08A, and it is impossible to detect the phase difference. Since this cable is not subject to the reference value, even if Icb reaches the reference value or more, it is judged as a charging current.

FIG. 12 is a diagram showing the current vector and the phase difference in the case of a ground fault with a capacitance of 1.5 μF, Cx0.4 μF, and a ground fault resistance of 796 Ω in the electric circuit. In this case, Iga is 2.50A, Icb is 0.71A, and the phase difference is 165 °, which is within the range of the ground fault determination standard. The ground fault resistance value is a ground fault resistance value when a 0-phase voltage of 80% is detected.

FIG. 13 is a diagram showing the phase difference with the current vector flowing through the ground line when the same cable has a ground fault with a ground fault resistance value of 796 Ω at another location. In this case, Icb is 0.71A and Ica is 0.25A, and the phase difference can be detected. The detected phase difference is 111 ° and is determined as a charging current.

Based on the above, the selection of the zero-phase current flowing through the ground wire of the high-voltage cable is a combination of a method of detecting and determining the phase difference of the current and a method of determining by setting a reference value for the cable whose phase difference is difficult to detect. I think it is possible if you do it. Further, since the reference value is set to 800 mA or more and the maximum charging current of the cable subject to the reference value is 249 mA, which is a considerable difference, it is considered that there is almost no risk that the detector makes a mistake in determining the reference value. Since the reference value is affected by the setting of the ground fault protection device on the substation side and the capacitance of the electric circuit, it is necessary to match the setting conditions on the substation side.

As described above, if the detector is provided with a zero-phase current sorting function, it can react to the ground fault current and not to the charging current. By doing so, it is possible to match the operation setting value of the detector with the setting value of the ground fault protection relay on the power supply side, and if the high voltage cable is interrupted by a high resistance ground fault, the detector will be sure. Can be improved to work. Therefore, in the search at the time of a ground fault, checking the display of the detector surely narrows the search range, which helps to reduce unnecessary time and labor required for the search.

Furthermore, if the data on which the detector operates is transmitted from the 21 external communication terminals to the maintenance organization that maintains the electrical equipment, the maintenance organization that receives the information can grasp the location and details of the accident, so that the recovery material can be promptly used. It will be possible to arrange and arrange the system and move to restoration work. By doing so, the labor and time required for accident search can be greatly reduced, and occupational accidents associated with the search work can be suppressed, so further effects can be expected.

It is a failure detector block circuit diagram which shows the example of 0-phase current selection by this invention. It is a ground fault current Ig and a voltage vector figure at the time of A phase ground fault. It is a vector diagram of A phase ground voltage Ega and charge current Ica. It is a composite vector diagram of the ground fault current Ig of the A phase and the charge current Ica. It is a vector diagram of the B-phase ground voltage Egb and the charge current Icb. FIG. 1 is a current phase difference at the time of a cable ground fault (Rg 200Ω). FIG. 2 is a current phase difference at the time of a cable ground fault (Rg 200Ω). It is a current phase difference-1 figure at the time of a cable ground fault (Rg2,389Ω). FIG. 2 is a current phase difference at the time of a cable ground fault (Rg2,389Ω). FIG. 3 is a current phase difference at the time of a cable ground fault (Rg 200Ω). It is a current phase difference diagram at the time of another place ground fault (Rg 200Ω). It is a current phase difference diagram at the time of a cable ground fault (Rg796Ω). It is a current phase difference diagram at the time of another place ground fault (Rg796Ω).

An embodiment according to this invention will be described with reference to FIG. 1 in FIG. 1 shows a 6,6 kV single-phase high-voltage distribution line. 2 indicates the high-voltage cable installed there, 3 indicates the shielding copper tape of the high-voltage cable, and 4 indicates the grounding wire of the high-voltage cable. 5-1 and 5-2 are 0-phase current transformers that detect the current flowing through the ground wire of each phase of the high-voltage cable.

The data detected by the 0-phase current transformers 5-1 and 5-2 are input to the waveform settling circuit 1 of 8.

In the waveform setting circuit 1 of 8, the harmonic component is removed from the data input from 5-1 and 5-2 to form a basic waveform, which is output to the effective value determination circuit of 10.

In the effective value determination circuit of 10, when there are two input current data, the effective values are compared to identify the phase of a large current, and the specified phase data and the two waveform data are combined with the phase difference determination circuit of 13. Output to. When there is only one input current data, the phase is specified, and the signal of the specified phase and the effective value data are output to the reference value determination circuit of 12.

The phase difference determination circuit 13 detects how much the small current is delayed from the input waveform data with reference to the large current. If the detected phase difference is in the range of 150 ° to 180 °, a large current is selected as the ground fault current, and the signal of the corresponding phase and the selected waveform data are output to the Is verification circuit of 14. If the phase difference is other than that, the related data is output to the 18 data storage circuits and the operation is stopped.

In the reference value determination circuit of 12, the effective value of the current input from the effective value determination circuit of 10 is compared with the value set by the reference value setting circuit of 7, and the value is input from the effective value determination circuit of 10. When the value is large, the signal of the corresponding phase and the drive signal are output to the display drive circuit of 15. The reference value in the reference value setting circuit is set to 400 mA, 500 mA, 600 mA, and 800 mA. To select the reference value, check the capacitance of the electric circuit and the setting of the ground fault protection device on the substation side, and select the appropriate value. If the cable to which the detector is attached is not subject to the reference value, the operation of the reference value setting circuit of 7 is turned off to suppress unnecessary response.

In the display drive circuit of 15, the corresponding phase of the display device of 16 is displayed by the data of the ground fault phase and the drive signal input from the reference value determination circuit of 12.

The 0-phase current transformer of 6 detects the 0-phase current flowing through the common ground line and inputs the data to the waveform setting circuit 2 of 9.

In the waveform setting circuit 2 of 9, the harmonic component is removed from the input current data to form a fundamental wave, which is output to the sensitivity setting circuit of 11.

In the sensitivity setting circuit of 11, if the effective value of the fundamental wave is equal to or more than the set value, the data is output to the Is verification circuit of 12. The set value is the operating current value of the detector, and can be set in four stages of 200 mA, 300 mA, 400 mA, and 500 mA, and each circuit is operated when a current value equal to or higher than the set value is detected.

In the Is verification circuit of 14, the waveform data input from the phase difference determination circuit of 13 and the waveform data input from the sensitivity setting circuit of 11 are verified. If the current value input from the phase difference determination circuit of 13 is larger than the current value input from the sensitivity setting circuit of 11, and the phase advances within 0 ° to 30 °, it is determined to be a ground fault current, and the display drive of 15. The drive signal of the corresponding phase is output to the circuit. If the current value input from the 13 phase difference determination circuits is small, or if the phase exceeds 30 °, it is determined to be a charging current, and the data is output to the 18 data storage circuits to operate the device. Stop.

In the display drive circuit of 15, when the drive signal of the phase display is received from the Is verification circuit of 14, the corresponding phase of the display device of 16 is displayed.

When the capacitance of the single-phase high-voltage distribution line 1 shown in FIG. 1 is 1 μF (for one phase) and the capacitance of the high-voltage cable 2 is 0.30 μF, the high-voltage cable ground fault and the ground fault at another location occur. The selection of ground fault current and charging current will be described. The setting of the ground fault protection device on the substation side shall be such that the high voltage circuit breaker opens when the detection of the 0-phase voltage reaches 80%. The set values and judgment criteria for each circuit of the detector are as follows. The reference value of the reference value setting circuit of No. 7 is 800 mA, and the capacitance of the cable subject to the reference value is 0.12 μF or less. The set value of the sensitivity setting circuit of 11 is 200 mA. The determination criteria of the phase difference determination circuit 13 is that if the large current advances from 150 ° to 180 °, the large current is determined to be the ground fault current, and otherwise it is determined to be the charging current. The determination standard of the Is verification circuit of No. 14 is that if a large current advances within 0 ° to 30 °, the current is determined to be a ground fault current, and otherwise it is determined to be a charging current. The detection current of each 0-phase current transformer shall be 200 mA or more.

In the embodiment, the capacitance of the high-voltage cable is 0.30 μF, so the cable is not subject to the reference value. Therefore, the reference value setting circuit is turned off.

Under the conditions of the embodiment, the Iga when a resistance ground fault of 100Ω occurs in the A-phase cable is 2.07A. This current is detected by the 0-phase current transformer 5-1. Further, a charging current Icb of 0.62A flows through the B-phase ground wire, and is detected by the 0-phase current transformer 5-2. These waveform data are input to the waveform settling circuit 1 of 8.

In the waveform setting circuit 1 of 8, the harmonic component is removed to form a fundamental wave, and the waveform is output to the effective value determination circuit of 10.

In the effective value determination circuit of 10, a large phase is specified. Since Iga is large, it is tentatively determined to be an A-phase ground fault, and two current waveforms are output to the phase difference determination circuit of 13 together with the signal of the A-phase ground fault.

In the phase difference determination circuit of 13, the phase difference is detected from the input Iga and Icb waveforms. Since Iga is large, the phase difference with Icb is detected with reference to it. The detected value is 179 °. 179 ° is within the ground fault determination standard (150 ° to 180 °), Iga is determined to be the ground fault current, and the waveform and the A-phase ground fault signal are output to the Is verification circuit of 14.

The 0-phase current transformer of 6 detects the combined current Igs (hereinafter referred to as “Igs”) 1.45A of Iga and Icb and inputs it to the waveform setting circuit 2 of 9.

In the waveform setting circuit 2 of 9, the input Igs waveform is formed as a fundamental wave, and the data is output to the sensitivity setting circuit of 11.

In the sensitivity setting circuit of 11, the effective value of the input Igs is determined. Since 1.45A has a set value of 200 mA or more, the Igs waveform data is output to the Is verification circuit of 14.

In the Is verification circuit of 14, the magnitude and phase of Igs input from the phase difference determination circuit of 13 and Igs input from the sensitivity setting circuit of 11 are verified. The size of Iga is 2.07A, the size of Igs is 1.45A, and the verification of the size is OK. Further, the phase difference is that Iga advances by 1 °. Since the determination result conforms to the determination criteria of the ground fault current, the drive signal of the A-phase ground fault is output to the display drive circuit of 15.

The display drive circuit of 15 receives the drive signal of the A-phase ground fault and drives the display device of 16 to display the A-phase ground fault.

Under the above ground fault conditions, it is possible to select the ground fault current. Explain whether the detector works properly when a ground fault occurs in another place under the same conditions.

When a ground fault with a ground fault resistance of 100Ω occurs at another location, a charging current Ica of 0.02A, an Icb of 0.62A, and a combined current of Ica and Icc (hereinafter referred to as "Ics") of 0.62A flow. .. Since Ica is less than 200 mA, it cannot be detected. Therefore, the data is output to the reference value determination circuit of 12 in the effective value determination circuit of 10.

In the reference value determination circuit of 12, since the setting of the reference value is OFF, the data is output to the data storage circuit of 18 as being excluded from the reference value, and the operation is stopped.

Next, when the cable has a ground fault with a ground fault resistance of 500Ω, Iga is 1.98A, Icb is 0.60A, and the combined current Igs is 1.38A. In the phase difference detection between Iga and Icb, Iga advances by 174 °. Further, the phase difference between Iga and Igs is that Iga advances by 3 °. Therefore, the relationship with Iga, Icb, and Igs in this case satisfies the determination criteria of the phase difference determination circuit of 13 and the Is verification circuit of 14, and Iga is selected as the ground fault current.

If a ground fault occurs at another location under the same conditions, Ica is 0.09A, Icb is 0.60A, and the combined current Ics is 0.59A. Since Ica is less than 200 mA, it cannot be detected. Further, since the cable is not subject to the reference value, the Icb data is output from the reference value determination circuit of 12 to the data storage circuit of 18, and the operation is stopped.

As the next ground fault condition, when the cable has a ground fault with a ground fault resistance of 1,194Ω, Iga is 1.67A, Icb is 0.53A, and the combined current Igs is 1.16A. The phase difference between Iga and Icb is that Iga advances by 166 °. Further, the phase difference between Iga and Igs is that Iga advances by 6 °. Therefore, the relationship with Iga, Icb, and Igs in this case satisfies the determination criteria of the phase difference determination circuit of 13 and the Is verification circuit of 14, and Iga is selected as the ground fault current. The ground fault resistance of 1,194Ω is a ground fault resistance value when a 0-phase voltage of 80% is generated.

When a ground fault occurs at another location under the above conditions, Ica is 0.19A, Icb is 0.53A, and the combined current Ics is 0.45A. Since Ica is less than 200 mA, there is a high possibility that it will be undetectable. However, if it is detected, the phase difference can be detected. In that case, the detected value is that Icb advances 111 ° from Ica. Therefore, the determination based on the phase difference determination standard is also a charging current. If the phase difference cannot be detected, the cable is processed as a cable that is not subject to the reference value. Therefore, the Icb data is output from the reference value determination circuit of 12 to the data storage circuit of 18, and the operation is stopped.

From the above, if the ground fault current and the charging current are selected, the set value of the 0-phase current transformer can be lowered, and a small ground fault current can be detected.

In the case of the conventional detector, since there is no zero-phase current selection function, the operating current must be set to a current value that exceeds the maximum charging current. Incidentally, the maximum charging current of the high-voltage cable of the embodiment is 0.62 A. Considering the influence of harmonics, it may be more than tripled, and its value exceeds 1.8A. The set value in such a case was set to 2A, but as a matter of course, it could not be detected for a ground fault current of less than 2A.

As described above, if the detector is provided with a function of selecting the ground fault current and the charging current, it is possible to accurately react to the ground fault current and suppress unnecessary operation with respect to the charging current. In the present invention, it is considered that a stable power supply is required in order to detect the current and operate various logic circuits accurately, and the power supply is considered to be an external power supply.

1 6.6kV single-phase high-voltage distribution line 2 High-voltage cable 3 Shielding copper tape for high-voltage cable 4 Common grounding wire for high-voltage cable 4-1 Grounding wire for high-voltage cable A phase 4-2 Grounding wire for high-voltage cable B phase 5-1 High-voltage cable Cable A-phase 0-phase current transformer 5-2 High-voltage cable B-phase 0-phase current transformer 6 High-voltage cable common ground wire 0-phase current transformer 7 Reference value setting circuit 8 Waveform settling circuit 1
9 Waveform settling circuit 2
10 Effective value judgment circuit 11 Sensitivity setting circuit 12 Reference value judgment circuit 13 Phase difference judgment circuit 14 Is verification circuit 15 Display drive circuit 16 Display device 17 Power supply circuit 18 Data storage circuit 19 Ground terminal 20 External power input terminal 21 External communication terminal 22 Detector housing

Claims (1)

In a single-phase high-voltage distribution line, when a high-voltage cable has a ground fault or a ground fault occurs elsewhere, the 0-phase current flowing in the ground line is detected to detect the phase difference, and the large current is larger than the smaller current. If the current is within 150 ° to 180 °, set a reference value for a device that sorts the current as a ground fault current, or for a cable that cannot detect the phase difference due to the small capacitance of the cable. A high-voltage cable failure detection device that sorts the current as a ground fault current when it detects a current above the standard value in the cable.

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