JPH0530646A - Method and apparatus for detecting ground fault section of distribution line - Google Patents

Abstract

PURPOSE:To make it possible to detect ground fault section easily with no misjudgment by judging ground fault information based on zero-phase higher harmonic components. CONSTITUTION:Each phase current is detected at the measuring point located at the end of each section of a distribution line and zero-phase higher harmonic components I<(n)> is determined through filtering based on the respective phase currents thus decising a ground fault. Upon decision of ground fault, phase difference between a zero-phase current 10 and a basic wave component I0<(1)> is determined with reference to predetermined phase voltages Vab, V0, Va. Ground fault point can be detected readily from the distribution of the phase difference theta at each measuring point.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention detects the ground fault information and the direction ground fault information by measuring the current of the distribution line at a terminal station provided for each fixed section on the distribution line to detect the ground fault of the distribution line. The present invention relates to a ground fault section detection method and a ground fault section detection apparatus for a distribution line capable of detecting a failure section.

[0002]

2. Description of the Related Art A distribution line is an electric line installed between a substation and a consumer, and generally a large number of distribution lines are drawn from one substation. Each distribution line is provided with a breaker for sending out provided inside the substation, and a division switch outside the substation at regular intervals.

When an accident such as a ground fault occurs in the middle of the distribution line, the circuit breaker is opened, and accordingly the section switch is also opened to protect the distribution line. In this case, the cause of the ground fault is investigated. Therefore, it is important to detect where the ground fault section is in order to supply power promptly other than the ground fault section. Therefore, in the past, the terminal station (may be provided at the same place as the division switch or at a different place at regular intervals of the distribution line. In addition, the number of the division switches does not match. Was good).

This terminal station has three current sensors for measuring the current of each phase (a, b, c phases) and three voltage sensors for measuring the voltage of each phase. The phase current I0 is calculated, and the zero phase voltage V0 is calculated from the three voltage sensors.
And calculate the phase difference between the zero-phase current I0 and the zero-phase voltage V0 and the phase difference between the zero-phase current I0 and the zero-phase voltage V0. It determines the ground fault information and sends it to the master station, and the master station is located between the terminal station that detected the ground fault in the direction of the substation and the terminal station that detected the ground fault in the direction of the load. It was assumed that the section to do is a ground fault section.

[0005]

When the ground fault information is determined, the magnitude of the zero-phase current itself, which is mostly the fundamental wave component, is determined. However, even if a ground fault occurs,
Ground-fault current (zero-phase current) with most of the fundamental wave component
Does not always appear. This is because in a ground fault (intermittent arc optical ground fault) that frequently repeats dielectric breakdown and its recovery at the failure point, such as a ground fault in a cable distribution line, the harmonic component of the ground fault current increases, The fundamental wave component is considerably reduced. Therefore, as in the past, if the determination was made based on the magnitude of the zero-phase current (fundamental wave component),
Even if a ground fault occurs, the fundamental wave component is small and it is difficult to make a proper judgment, which often leads to an erroneous judgment.

An object of the present invention is to enable more reliable ground fault determination as compared with the conventional one, and to easily know a ground fault fault section when a ground fault is determined. It is an object of the present invention to provide a method of detecting a ground fault fault section and a ground fault fault section detection device for a distribution line.

[0007]

A method of detecting a ground fault section of a distribution line according to claim 1 for achieving the above object,
The distribution line is divided into multiple sections, the phase currents of the distribution line are detected at the measurement points in each section, the zero-phase current is determined based on these detected currents, and the harmonic component of the zero-phase current is the threshold value. When the voltage exceeds the fundamental wave component of the zero-phase current, the voltage of any of the phases a, b, and c of the distribution line obtained at the measurement point, the positive-phase voltage, the negative-phase voltage, the zero-phase voltage, or the predetermined voltage. The phase difference with the line voltage between the two phases is calculated, the distribution of the phase difference calculated at each measurement point along the distribution line is obtained, and the phase difference exists between the measurement points where the phase difference changes by approximately 180 °. This is a method of determining the section as a ground fault section.

According to a second aspect of the present invention, there is provided a ground fault fault section detection method for a distribution line, wherein the zero-phase harmonic component is calculated and then summed after the harmonic components of the respective phase currents are calculated. A ground fault fault section detection device for a distribution line according to claim 3 for achieving the above object, wherein a terminal station is arranged in each section of the distribution line divided into a plurality of sections, and each terminal station has the terminal station concerned. A transmitting means for transmitting the data obtained in step (1) is further provided, and a master station for receiving the data from the terminal station is arranged, and the terminal station is provided with means (a) to (g) among the following means (a) to (g): The means (g) is provided in the parent station and the other means (b) to (f) are provided in either the terminal station or the parent station. (a) Current sensor that detects each phase current of the distribution line at the measurement point in each section, (b) Zero-phase current detection means that calculates the zero-phase current based on the current detected by the current sensor, (c) The zero-phase current Means for calculating the harmonic component of ,, (d) means for calculating the fundamental wave component of the zero-phase current,
(e) The zero-phase harmonic component calculated by the means of (c) is compared with a threshold value, and when the threshold value is exceeded, a ground fault determination means for determining that there is a ground fault, (f) When a ground fault is judged by the ground fault judging means, the fundamental wave component of the zero-phase current obtained by the means of (d) and a, b, c of the distribution line obtained at the measurement point Phase difference calculation means for calculating the phase difference between the voltage of any phase, the positive phase voltage, the negative phase voltage or the zero phase voltage or the line voltage between the predetermined two phases, (g) detected by the calculation means of each terminal station Based on the distribution of the phase difference included in the phase difference data thus obtained, the phase difference is approximately 18
A ground fault section determining unit that distinguishes terminal station groups that differ by 0 ° and determines a section existing between mutually adjacent terminal stations in the distinguished terminal station groups as a ground fault failure section of the distribution line.

The ground fault section detecting device for a distribution line according to claim 4 has means for calculating a zero-phase harmonic component by the method according to claim 2, and the ground fault according to claim 3 is also provided. It has the same configuration as the faulty fault section detection device.

[0010]

According to the present invention, the ground fault of the distribution line can be detected by detecting the change of the zero-phase harmonic component, and the ground fault has occurred in the distribution line. In this case, the fundamental wave component of the zero-phase current and the voltage of any phase of a, b, or c of the distribution line obtained at the measurement point, the positive-phase voltage, the negative-phase voltage, or the zero-phase voltage, or between two predetermined phases A terminal station group that detects the ground fault point in the direction in which the power transmission end exists by utilizing the fact that the phase difference θ with the line voltage is reversed by about 180 ° depending on the positional relationship between the ground fault point and the terminal station. The terminal station group that detects a ground fault in the direction opposite to the direction in which the power transmission end exists is distinguished, and the section located between adjacent ones of these distinguished terminal stations is the ground fault fault section of the distribution line. Can be determined as

This will be described in detail. FIG. 2 is a diagram showing a three-phase distribution line, and it is assumed that, for example, a ground fault (ground fault resistance Rg) occurs in the a phase. FIG. 3 shows a well-known equivalent circuit using the symmetric coordinate method. In FIG. 3, the power source Ea appears only in the positive phase circuit, and does not appear in the zero phase circuit and the negative phase circuit. Neutral resistance R in the zero-phase circuit
Although there is n, this resistance value may be sufficiently larger than the ground impedance and may be infinite. The impedance on the power supply side as seen from the ground fault point and the impedance on the load side as seen from the ground fault point are determined by the ground capacitances C1 and C2. The ground fault resistance is equivalently 3Rg, and the equivalent ground fault current (1/3) Ig flows. This current flows through the power source side with low impedance in the positive-phase circuit and negative-phase circuit, but in the zero-phase circuit the impedance on the power source side from the ground fault point and the load side impedance from the ground fault point. According to, the shunt is made at the ground fault point.

The current sensors provided at the terminal stations existing on both sides of the ground fault set point are CT1 and CT2. In a normal state with no ground fault, the zero-phase current I0 is 0 and the negative-phase current I
2 is 0, and the positive-phase current I1 is I1 = jωC2Ea.

When a ground fault occurs, the zero-phase voltage V0 at the ground fault point is represented by V0 = -Ea / (1 + 3jωCRg), and the ground fault current is represented by Ig = jωCEa / (1 + 3jωCRg). Where C = C1 + C2. Zero-phase current I0, positive-phase current I1 and negative-phase current I2
The one detected by the current sensor CT1 is: I0 = C1 Ig / 3C (1) I1 = jωC2 Ea + Ig / 3 I2 = Ig / 3, and the one detected by the current sensor CT2 is I0 = -C2 Ig / 3C (2) I1 = jωC2 Ea I2 = 0.

From the expressions (1) and (2), the current sensors CT1 and CT2 detect a zero-phase current of some magnitude when a ground fault occurs. Here, focusing on a harmonic component of a specific order n (when the harmonic component is represented, a subscript ⁽ⁿ⁾ is attached), since the power source Ea supplies only the fundamental wave, Ea ⁽ⁿ⁾ = 0 You can save it. On the contrary, the ground fault becomes a harmonic generation source.
In particular, when there is a ground fault (intermittent isolated ground fault) in which breakdown and recovery are frequently repeated at the fault point, such as a ground fault that occurs in a cable distribution line, the ground fault current becomes a needle wave, It contains a large amount of high frequency components. Therefore, an equivalent circuit focusing on the harmonic components is as shown in FIG.

In FIG. 1, the zero-phase harmonic component I0 ⁽ⁿ⁾ and the positive-phase harmonic component I1 are normal when there is no ground fault.
⁽ⁿ⁾ and the anti-phase harmonic component I2 ⁽ⁿ⁾ are all 0 if the power source does not contain the harmonic component. When there is a ground fault, the zero-phase harmonic component I0 ⁽ⁿ⁾ , the positive-phase harmonic component I1 ^(n), and the negative-phase harmonic component I2 ⁽ⁿ⁾ are detected by the current sensor CT1 and are the harmonics of the power supply voltage. Since the component Ea ⁽ⁿ⁾ = 0, I0 ⁽ⁿ⁾ = C1 Ig ⁽ⁿ⁾ / 3C (3) I1 ⁽ⁿ⁾ = Ig ⁽ⁿ⁾ / 3I2 ⁽ⁿ⁾ = Ig ⁽ⁿ⁾ / 3 What is detected by the current sensor CT2 is I0 ⁽ⁿ⁾ =-C2Ig ⁽ⁿ⁾ / 3C (4) I1 ⁽ⁿ⁾ = 0 I2 ⁽ⁿ⁾ = 0.

From the equations (3) and (4), what is
Zero-phase harmonic component I0 of a certain magnitude ⁽ⁿ⁾To appear
Become. Therefore, this zero-phase harmonic component I0⁽ⁿ⁾To change
If the occurrence of a ground fault is detected, the ground fault can be detected with high sensitivity.
Can be issued. Also, after detecting a ground fault,
As can be seen from Eqs. (1) and (2), ground fault points and measurement points
The phase of the zero-phase current is reversed depending on the positional relationship with
Pay attention to. That is, both the terminal station T1 and the terminal station T2
An element having a common phase, such as the distribution obtained at the measurement point
Voltage of any phase of wire a, b, c, positive phase voltage, negative phase
Voltage or zero-phase voltage or line voltage between two specified phases
Then, calculate the relative phase difference between it and the fundamental wave component of the zero-phase current.
If you send it to the master station and send it to the master station,
The basis of the zero-phase current contained in the data received from the station
Presence of the transmitting end based on the distribution of the phase difference with the wave component
There is a terminal station group that detects a ground fault in the direction and a power transmission end
Distinguish from terminal stations that detect ground faults in the opposite direction
Therefore, it is possible to
The section located between the two is called the ground fault section of the distribution line.
Can be decided.

[0017]

Embodiments will be described in detail below with reference to the accompanying drawings showing embodiments. FIG. 4 is a distribution system diagram. The distribution substation 1 is provided with a transformer 11 with a Δ-Δ connection.
The electric power stepped down to 6.6 kV by the electric power source 1 passes through the circuit breakers 3a, 3b, ...
a, 4b, ... Distribution lines 4a, 4b, ...
Are connected to transformers 5a1, 5a2, ..., 5b1, 5b2, ... With Y-Y connection for distributing electric power to consumers, and each transformer 5a1, 5a2 ,. ... near the terminal stations 7a1, 7
a2, ..., 7b1, 7b2 ,.

Each of the terminal stations 7a1, 7a2, ... Has the same configuration, and each phase current information extracted from CT1, CT2, CT3 for detecting the current of each phase and the transformers 5a1, 5a2 ,.・
.. Information on line voltage between phases ab extracted from
The line voltage between the phases is the one used for the driving power source of the terminal station, and it is not necessary to newly install the voltage sensor).
, Calculation processing for calculating the phase difference θ between the line voltage Vab and the harmonic component of the negative phase current I2, the harmonic component of the zero phase current I0 and the fundamental wave component of the zero phase current I0, and determining the ground fault, short circuit or disconnection Part 7
1 and a transmission unit 72 that transmits the determination result obtained by the arithmetic processing unit 71 to the master station 9 (see FIG. 8) as 4-bit data.

As shown in FIG. 5, the arithmetic processing unit 71 includes an adder circuit 716 for calculating the value of the zero-phase current, a sample hold circuit 711 for sampling the value of the a-phase current Ia, and b.
A sample and hold circuit 712 that samples the value of the phase current Ib, a sample and hold circuit 713 that samples the value of the c phase current Ic, a sample and hold circuit 714 that samples the value of the zero phase current I0, and a value of the line voltage Vab. A sample-hold circuit 715 for sampling the sample and hold values, and a multiplexer 720 that outputs sampled and held values arranged in time order and a multiplexer 720.
Conversion circuit 730 for A / D converting the data output from the
And digitally operating the A / D converted data, the line voltage Vab, the phase currents Ia, Ib, Ic, the zero-phase current I0, the positive-phase current I1, the magnitude of the negative-phase current I2, and the zero-phase current I0. Of the ground fault based on the calculation data of the calculation circuit 740, which calculates the phase difference θ between the line voltage Vab and the fundamental wave component of the zero-phase current I0 while calculating the harmonic component and the fundamental wave component of And a judgment circuit 750 for judging short circuit or disconnection.

Further, the arithmetic processing unit 71 is configured to detect the line voltage Vab
A fundamental wave pulse generation circuit 760 that generates a fundamental wave pulse for each cycle of, and a frequency divider 761 that divides the pulse thus generated at a predetermined frequency division ratio (for example, 1/12 times),
Based on the output pulse of the frequency divider 762 and the frequency divider 762 that divides the frequency division ratio of the frequency divider 761 by a finer frequency division ratio (for example, 1/60 times) divided by the number of sample and hold circuits. The calculation circuit 740 has a switching controller 763 for supplying a switching control signal to the sample and hold circuits 711 to 715.
Calculation is performed using the 61 output pulse as a synchronization signal.

As a method of calculating the magnitude of the current or voltage and the phase angle by the calculation circuit 740, a conventionally known method can be used. For example, the magnitude can be obtained by obtaining the Fourier sine component and the Fourier cosine component over one period and taking the root mean square of both components. Further, the phase angle can be obtained by taking tan ⁻¹ of the ratio of the Fourier sine component and the Fourier cosine component. To calculate the harmonic component, for example, the filter operation I0 ⁽ⁿ⁾ = (1 / T) ∫I0exp (-jnωt) dt [0 <t <T] is performed on the zero-phase current I0. The harmonic component I0 ⁽ⁿ⁾ may be obtained.

Similarly, if I 0 ⁽¹⁾ when n = 1 is obtained, the fundamental wave component of the zero-phase current can be obtained. Furthermore, although the above example is for obtaining a specific single order harmonic component, two or more specific harmonic components (for example, n =
It is preferable to select a multiple of 3, such as 9, 12, and 15. ) Is calculated, and the effective value I0 ^(HF) = (I0 ^{(9) 2} + I0 ^{(12) 2} + I0 ^{(15) 2} ) ^1/2 is calculated to determine whether or not the threshold value is exceeded. Good. In this manner, by adding a large number of harmonic components, the detection sensitivity can be improved as compared with the case of determining only a single harmonic component.

FIG. 6 is a flow chart showing the procedure of the judgment circuit 750 for judging a ground fault, a short circuit, and a disconnection. According to FIG. 6, the determination circuit 750 makes a short-circuit determination (step (1)) based on various data supplied from the calculation circuit 740.
Is transmitted to the transmission unit 72. A well-known method can be adopted as the short circuit determination method.

If it is judged that it is not a short circuit, a disconnection judgment (step (2)) is carried out, and if it is judged that it is a disconnection, the code "0010" representing the disconnection is sent out. A well-known method can be adopted as the disconnection determination method. If it is determined that the line is not broken, the ground fault is determined (steps (3) and (4)).
In step (3), the zero-phase harmonic component I0 ^{(n) is set} to the threshold value k.
compared ^(n), and if it exceeds but the threshold k ^(n), step
In (4), the phase difference θ between the line voltage Vab and the fundamental wave component I0 ⁽¹⁾ of the zero-phase current I0 is 360 ° divided into eight regions I, II, ..., VIII (see FIG. 7). ) Is entered, and the corresponding code is transmitted in step (7).
For example, if 0 <θ ≦ π / 4, the region I is entered, so the code is “1”.
000 ”is sent. If π / 4 <θ ≦ π / 2, area II
Since it enters, the code "1001" is transmitted. In addition, the ground fault judgment in steps (3) and (4) means the judgment of one-line ground fault, and in the case of two-wire ground fault and three-wire ground fault, it can be judged by the short-circuit judgment of step (1). Therefore, 2-wire ground fault and 3-wire ground fault are not determined in steps (3) and (4).

If it is determined that there is no ground fault, the code "0000" indicating no failure is transmitted in step (8). The transmitter 72 sends the code received from the determination circuit 750 to the master station 9,
Send via wireless, light, infrared or other medium (step
(9)). As shown in FIG. 8, the master station 9 includes a receiving section 91 and a failure section determining section 92.

The failure section determination unit 92 of the master station 9 determines in which section the ground fault has occurred based on the code received from the transmission unit 72 of each terminal through a medium such as radio, light, or infrared. The determination method is as follows. Terminal stations 7a1, ..., 7a6 along the distribution line as shown in FIG.
Suppose that is arranged.

When a one-line ground fault occurs between the terminal station 7a3 and the terminal station 7a4 (see FIG. 9), the line spacing sent from the terminal stations 7a1, 7a2, 7a3 on the power transmission side from the ground fault point. Voltage Vab
And the region showing the phase difference θ between the fundamental wave component I0 ⁽¹⁾ of the zero-phase current I0 is the same region or two regions adjacent to each other (for example, regions I and VIII in FIG. 7). However, the region showing the phase difference θ between the line voltage Vab sent from the terminal stations 7a4, 7a5, 7a6 on the load side from the ground fault and the fundamental wave component I0 ⁽¹⁾ of the zero-phase current I0 is the region I. This is a region (regions V and IV in FIG. 7) that is shifted by about 180 ° compared with. Therefore, the master station 9 knows that a ground fault has occurred between the terminal station 7a3 and the terminal station 7a4 before and after the phase difference region is largely deviated. Since all directions are divided into eight areas in this way, the transmission line between the terminal station and the master station may send data indicating which of these eight areas the phase angle falls into. Therefore, it is not necessary to send the phase angle data as it is, and it is possible to prevent the capacity of the transmission line from increasing. If the capacity of the transmission line is fixed, the capacity allocated to other data can be increased.

Although the present invention has been described based on the embodiments, the present invention is not limited to the above embodiments. Although the line voltage Vab between the ab phases is used in the above-mentioned embodiment, it may be compared with the voltage of any phase, the positive phase voltage, the negative phase voltage or the zero phase voltage. in this case,
Since the existing voltage sensor cannot be used, it is necessary to provide one to three dedicated ones.

Further, according to FIG. 7, all directions are divided into eight areas, but in consideration of the overlap with the adjacent areas, it is practical if the area is divided into at least five areas. Further, in the above embodiment, the harmonic component is calculated from the zero-phase current, but for a specific harmonic order n, the following formula Ia ⁽ⁿ⁾ = (1 / T) ∫Ia exp (-jnωt) dt [0 <t <T] Ib ⁽ⁿ⁾ = (1 / T) ∫Ib exp (-jnωt) dt [0 <t <T] Ic ⁽ⁿ⁾ = (1 / T) ∫Ic exp (-jnωt) The harmonic component of each phase current is calculated using dt [0 <t <T], and the zero-phase harmonic component I0 ^{(n )} is calculated using the formula I0 ⁽ⁿ⁾ = Ia ⁽ⁿ⁾ + Ib ⁽ⁿ⁾ + Ic ^{(n). )} May be asked.

In each of the above embodiments, the terminal station 7a1,
Although the calculation circuit 740 and the determination circuit 750 are provided in 7a2, ..., 7b1, 7b2, ..., They may be provided in the master station 9. In this case, the transmission unit 72 of the terminal station transmits the measured current data to the master station 9, and the master station collects and determines the data of each terminal station. In addition to this, various modifications can be made without departing from the spirit of the present invention.

[0031]

As described above, according to the invention of the method of detecting a ground fault in a distribution line according to claims 1 and 2, when the ground fault information is determined, it is determined by the zero-phase harmonic component. Therefore, the possibility of erroneous determination is reduced, and when a ground fault is determined, the ground fault fault section can be easily known.

According to the invention of the ground fault section detecting device for a distribution line of claims 3 and 4, each phase current is detected at the measurement point at the end of each section of the distribution line and based on the zero phase harmonic component. The ground fault can be determined with high sensitivity.When the ground fault is determined, the phase difference with the fundamental wave component of the zero-phase current is calculated based on the phase of the voltage of the predetermined phase, and each of the phase differences is determined. The ground fault point can be easily detected from the distribution over the measurement points.

[Brief description of drawings]

FIG. 1 is a symmetrical three-phase equivalent circuit diagram focusing on harmonic components of a distribution line in which a ground fault has occurred, for explaining the principle of the present invention.

FIG. 2 is a circuit diagram of a distribution line in which a ground fault has occurred.

FIG. 3 is a symmetrical three-phase equivalent circuit diagram of a distribution line in which a ground fault has occurred.

FIG. 4 is a distribution system diagram in which terminal stations are arranged.

FIG. 5 is a block diagram showing an internal configuration of an arithmetic processing unit provided in a terminal station.

FIG. 6 is a flowchart showing a procedure for determining a ground fault, a short circuit, and a disconnection performed by a determination circuit 750.

FIG. 7 is a diagram in which all directions are divided into eight regions to classify phase angles.

FIG. 8 is a block diagram showing a main configuration of a master station.

FIG. 9 is a distribution line diagram for explaining a method of determining a ground fault section of the distribution line.

[Explanation of symbols]

4a, 4b distribution line 7a1, 7a2, 7b1, 7b1 terminal stations 72 Transmitter 740 Calculation circuit 9 parent station 92 Ground fault section determination unit Regions I to VIII CT1, CT2, CT3 Current sensor

Claims (4)

[Claims] 1. A distribution line is divided into a plurality of sections, each phase current of the distribution line is detected at a measurement point in each section, a zero-phase current is obtained based on these detected currents, and harmonics of the zero-phase current are obtained. The component is calculated, the zero-phase harmonic component is compared with the threshold value, and when the threshold value is exceeded, the fundamental wave component of the zero-phase current and a, b, c of the distribution line obtained at the measurement point Voltage of any phase, positive phase voltage, negative phase voltage or zero phase voltage or predetermined 2
A phase difference between the phase and the line voltage is calculated, the distribution of the phase difference calculated at each measurement point along the distribution line is obtained, and a section existing between the measurement points at which the phase difference changes by approximately 180 ° Is determined as a ground fault section, and a ground fault section detection method for a distribution line. 2. A distribution line is divided into a plurality of sections, each phase current of the distribution line is detected at a measurement point in each section, a harmonic component of each phase current of the distribution line is calculated, and the harmonic components are calculated. Calculate the zero-phase harmonic component by summing, compare the zero-phase harmonic component with the threshold value, and if the value exceeds the threshold value, the fundamental wave component of the zero-phase current and the distribution obtained at the measurement point. Calculate the phase difference between the voltage of any one of the a, b, and c phases of the wire, the positive phase voltage, the negative phase voltage, or the zero phase voltage, or the line voltage between the specified two phases, and measure each point along the distribution line. The distribution of the phase difference calculated in 1. is determined, and the section existing between the measurement points at which the phase difference changes by approximately 180 ° is determined as the ground fault section. Method. 3. A ground fault section detecting device for a distribution line, which detects a ground fault by a zero-phase current flowing through the distribution line, and detects a ground fault section when the ground fault is detected. Then, a terminal station is arranged in each section of the distribution line divided into a plurality of sections, each terminal station is provided with a transmitting means for transmitting the data obtained by the terminal station, and the data is received from the terminal station. A master station is installed to do this, the terminal station is provided with means (a) of the following means (a) to (g), the master station is provided with means (g), and other means (b) to (g). f) is a ground fault section detecting device for the distribution line, which is provided in either the terminal station or the master station. (a) Current sensor that detects each phase current of the distribution line at the measurement point in each section, (b) Zero-phase current detection means that calculates the zero-phase current based on the current detected by the current sensor, (c) The zero-phase current Means for calculating the harmonic component of, (d) means for calculating the fundamental wave component of the zero-phase current, (e) comparing the zero-phase harmonic component calculated by the means of (c) above with a threshold value. If the threshold value is exceeded, a ground fault determining means for determining that there is a ground fault fault, (f) If a ground fault is determined by the ground fault determining means,
The fundamental wave component of the zero-phase current obtained by means of (d) and the voltage of any of a, b, or c phases of the distribution line obtained at the measurement point, positive-phase voltage, negative-phase voltage, or zero-phase voltage Or predetermined 2
Phase difference calculating means for calculating the phase difference with the line voltage between the phases, (g) based on the distribution of the phase difference contained in the data of the phase difference detected by the calculating means of each terminal station, the phase difference is A ground fault section determining unit that distinguishes terminal station groups that differ by approximately 180 °, and determines a section that exists between adjacent terminal stations of these distinguished terminal station groups as a ground fault failure section of the distribution line. 4. A means for calculating a harmonic component of each phase current of a distribution line, and a calculating means for summing the calculated phase harmonic components, in place of the means of (c), The ground fault judging means of (e) compares the value of the zero-phase harmonic component added by the calculating means with the threshold value, and when the value exceeds the threshold value,
The ground fault section detecting device for a distribution line according to claim 3, which determines whether there is a ground fault.