JPH1048286A - Method and apparatus for locating ground fault section of isolated overhead transmission line - Google Patents

Abstract

PROBLEM TO BE SOLVED: To estimate the occurring direction of fault by estimating a zero-phase current to be detected by a current sensor provided on a transmission line based on a zero-phase voltage upon occurrence of a fault on an isolated transmission line. SOLUTION: A transmission line of phases A-C is connected between a power supply and a load and current detectors are provided respectively. A three-phase synthesizing section 41 synthesizes a zero-phase current IO and the phase ϕIO thereof from detected current values IA-IC of respective phases and a threshold processing section 42 transmits occurrence of failure to a decision section 45 when the zero-phase current IO exceeds a threshold level. A level converting section 43 converts the current values IA-IC into current values Ia-Ic of same level as the zero-phase current IO. A phase difference calculating section 44 determines the phase difference between the zero-phase current IO and the current values Ia-Ic and then determines a phase current for generating a phase difference of about 90 deg. thus specifying a faulty phase. A decision section 45 decides that the failure occurred on the load side when the zero-phase current IO leads the current of faulty phase otherwise decides that the failure occurred on the power supply side and notifies the fact to a fault center through a modem 46.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ungrounded overhead transmission line for specifying the location of an accident location in an ungrounded three-phase overhead transmission line when the accident occurs. The present invention relates to a method and apparatus for locating a ground fault section of a transmission line.

[0002]

2. Description of the Related Art Hitherto, fault location of an ungrounded overhead transmission line has been carried out, for example, in a state where the entire overhead transmission line is cut off from the ground and supported by a telephone pole or the like. A fault section locating device for ungrounded transmission lines as shown in Fig. 11 and Fig. 12 has been proposed (Japanese Patent Application No. 5-60 / 1990).
No. 217, Japanese Patent Application No. 6-82536). First, in the case of Japanese Patent Application No. 5-60217, as shown in FIG. 11, the magnitudes of the zero-phase currents (IOA, IOB) and the zero-phase currents are provided at points A and B on the transmission line 61 connecting the power supply 64 and the load 65. Detectors 62A and 62B for detecting the phases (φOA and φOB) of the phase currents are provided, and central device 63 detects the phase of the zero-phase current and the phase of the zero-phase current detected by detectors 62A and 62B. The section where the ground fault occurs is located. Transmission line 61
FIG. 11 schematically shows one line.
Because it is a phase exchange, it consists of three transmission lines,
It is needless to say that the current of each of the three transmission lines is measured at points A and B. The ground height of the transmission line 61 is around 10 to 30 m, and the zero-phase current flowing when a ground fault occurs in such a line configuration is about 0.08 A per km, ignoring the resistance at the ground fault point. , And is proportional to the line length. The current detection level of the current ungrounded transmission line FL device is 0.4 A, and the distance from the sensor to the end of the line must be 5 km or more to make the magnitude of the zero-phase current at the measurement point 0.4 A or more. In reality, considering that the ground fault resistance is high, the condition is to detect even if the ground fault current is reduced to 1/2, so the distance from the sensor to the line end must be 10 km or more. Become. That is, the distance between the power supply 64 and the point A and the distance between the point B and the load 65 are set to 10
km or more. Further, in the current system, since the algorithm locates a section based on a comparison result of information on different points, two or more sensor installation points are required. Therefore, in order to obtain a signal level sufficient for information comparison (to clearly determine the difference in the magnitude of the zero-phase current at both measurement points), the distance between the sensors (between point A and point B) also needs to be about 10 km. Therefore, the applicable condition of the line length of the FL system at two sensor locations is 30 km or more.
Japanese Patent Application No. 6-82536 discloses a method in which the discrimination device is installed at one location regardless of the conditions of the track system to enable discrimination of the direction of the accident. As shown in FIG. A voltage sensor 73 for detecting a voltage between a flat or curved plate-shaped electrode 71 facing the overhead power transmission line 70 in a non-contact manner and insulated from a tower in the vicinity of a connection portion between the power transmission line 80 and the underground transmission line 80; A zero-phase voltage and a zero-phase current are detected from a current sensor 81 installed on an underground power transmission line 80 near the connection portion, and the phases are compared to determine a failure direction by a determination device 90. In addition, 91 is a solar cell.

[0003]

The ungrounded overhead transmission line shown in FIG. 11 has a relatively low transmission voltage of, for example, 33 kv or the like, and some transmission lines have a length of less than 30 km. It was necessary to determine the section of the ground fault. However, in the conventional orientation method, since the zero-phase current must be detected at the points A and B, it is essential that the length of the transmission line is 30 km or more. The method of locating the accident section of the track was extremely difficult and practically impossible. In the case of installation near the center of the transmission line, since the detected current values are almost the same, it is not possible to identify on which side the accident occurred. Further, although the discrimination device shown in FIG. 12 can discriminate the accident direction at one place, it needs two types of information of voltage and current, and as a result, the number of sensors increases,
As the cost of the apparatus increases, it is necessary to increase the processing capacity of the processing apparatus in order to process the increased information, and there is a problem that power consumption increases and power supply cost increases.

[0004]

SUMMARY OF THE INVENTION The present inventors have proposed various methods for solving the above-mentioned problems, that is, a method capable of locating the location of an accident from one piece of information without increasing the number of sensors. As a result of the study, we found a method that can locate the fault section using only current information without using voltage information. The points of interest are roughly divided into two: the relationship between the detection level of the zero-phase current and the measurement point, and the relationship between the phase of the zero-phase current and the fault phase current. 1. Level (A) The level of Io detected differs depending on whether the accident occurs before or after the measurement point. If the accident location is either one of the front and rear sides with respect to the measurement point, the value of Io is almost constant regardless of the location. (B) The closer the measurement point is to one end, the greater the difference in Io level detected when an accident occurs before and after the measurement point, and the shorter the distance between the measurement point and the line end is, the more the accident occurs. The detected zero-phase current is longer on the long side than the zero-phase current at the time of the accident. However, as the measurement point is closer to the center, the difference is smaller. 2. Regarding the phase (C) In an ungrounded three-phase overhead power transmission line system, the power factor is usually set to 0.9 or more, so that the phase difference α between the phase voltage and the phase current at all times is a voltage vector. On the other hand, the current vector must be delayed within 25 degrees. (D) In an ungrounded three-phase overhead power transmission line system, in a very rare case, when a no-load condition or a capacitor on the load side becomes relatively large, the phase current Ia becomes faster than the phase voltage Va. There is a possibility. (E) In consideration of the above (C) and (D), the non-grounding type 3
When an accident occurs in the phase overhead transmission line system, as shown in FIGS.
g flows. This ground current Ig and the observation points ZCT1 and ZCT1
Since the zero-phase currents I01 and I02 in CT2 are in-phase and anti-phase, and the phase vectors are parallel, the phase difference between the zero-phase currents I01 and I02 and the current Ia in the accident phase is 90 ° ± power factor phase difference. α. In actual operation, the phase difference α between the voltage and the current is expected to be usually 25 degrees or less from the relation that the power factor is set to 0.9 or more. In other words, the phase of the zero-phase current at the fault point and the phase of the current in the fault phase are determined by utilizing the fact that the difference produces a right angle ± α (α = phase difference due to the power factor). Of the method and apparatus for locating a ground fault accident section described above.

The present invention estimates a zero-phase current to be detected by a current sensor installed on a transmission line based on a zero-phase voltage when an accident occurs in an ungrounded transmission line. By comparing with the zero-sequence current obtained by
This is a method for locating the ground fault of an ungrounded overhead transmission line characterized by estimating the direction in which the accident occurred, but based on the zero-phase voltage detected at the time of the accident,
Two types of current are estimated for the case where an accident occurs on the longer line and the case where an accident occurs on the shorter line, and depending on which one of the currents detected at the time of the accident is closer,
This is to estimate the direction of the accident. In particular, when the two types of estimated zero-phase current values are close to the larger one, it is determined that an accident has occurred on the short transmission line side, and when the values are close to the smaller one, the fault is determined on the longer transmission line side. It is determined that an accident has occurred. Also, despite the accident in the ungrounded transmission line, the current sensor device installed in the middle of the transmission line was below its trigger level,
If the zero-phase current cannot be detected, and if the zero-phase current estimated when the short side of the overhead power transmission line is assumed to have an accident is estimated to be greater than the trigger level, the line It is determined that an accident has occurred on the long side of the ground, and if the estimated current value is equal to or lower than the trigger level, the grounding cannot be performed.

According to the present invention, when a zero-phase current exceeding a certain threshold value is detected at a current detection point of an ungrounded three-phase overhead power transmission line when the overhead power transmission line has an accident, When it is determined that an accident has occurred on the side where the distance between the current detection point and the end of the overhead power transmission line is short, and a zero-phase current exceeding the predetermined threshold has not been detected, the current detection point and A method of locating a ground fault section of an ungrounded overhead transmission line, comprising determining that an accident has occurred on a side having a long distance to an end of the overhead transmission line. In addition, the present invention provides a method for controlling the phase of a zero-phase current exceeding a certain threshold at the time of an accident when an accident occurs in an ungrounded three-phase overhead power transmission line.
The phase of the current causing the phase shift of ° is recognized as the fault phase, and the phase of the zero-phase current is on the load side when the phase of the current of the fault phase is ahead of the phase of the fault phase. If it is late, it is judged that there was an accident on the power supply side,
Indicate the accident direction on the spot if necessary, or
A method and an apparatus for locating a ground fault accident section of an ungrounded overhead transmission line in which such information is tabulated and displayed at a specific location using a communication line.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention relates to a method for detecting an accident in an overhead transmission line at a current detection point of an ungrounded three-phase overhead transmission line by comparing the information with the accident information received from a substation of the transmission line. If there is, based on the zero-sequence voltage, while estimating the zero-sequence current to be detected by the current sensor installed on the transmission line,
By comparing with the zero-phase current obtained by the current sensor at the time of the accident, it is a ground fault accident localization method of the ungrounded overhead transmission line characterized by estimating the direction of occurrence of the accident, Based on the zero-sequence voltage detected at the time of the accident, two types of currents are estimated from the case where the accident occurs on the longer line and the case where the accident occurs on the shorter line, starting from the sensor installation location. The direction of the accident occurrence is estimated based on which of the currents detected at the time of the accident was closer. If the two estimated zero-phase current values were closer to the larger one, the accident occurred on the short transmission line side. And when it is closer to the smaller one, it is determined that an accident has occurred on the longer transmission line side. Further, in the case where the zero-phase current could not be detected because the current sensor device installed in the middle of the transmission line was at or below its trigger level despite an accident in the ungrounded transmission line, If the zero-phase current estimated when it is assumed that an accident has occurred on the short side of the wire is estimated to be greater than the trigger level, it is determined that an accident has occurred on the long side of the line, and the estimated current If the value is equal to or lower than the trigger level, the orientation is disabled.

When a zero-phase current exceeding a predetermined threshold value is detected, it is determined that an accident has occurred on the side where the distance between the current detection point and the end of the overhead transmission line is short, and When a zero-phase current exceeding the threshold value is not detected, the distance between the current detection point and the end of the overhead transmission line is determined to have an accident on the long side. This is a ground fault accident section locating method, and the threshold value is a set value between two types of zero-phase current detected at a current detection point of an ungrounded three-phase overhead power transmission line. Still further, the present invention relates to a method for detecting a phase of a zero-phase current exceeding a predetermined threshold value and a phase of a current having a phase shift of about 90 ° at a current detection point of an ungrounded three-phase overhead power transmission line. When the phase of the zero-phase current is ahead of the phase of the current in the fault phase, the fault is on the load side, and when the phase of the zero-phase current is late, the fault is on the power source side. By using the method of locating the ground fault section of an ungrounded overhead transmission line, which is characterized by making judgments, the accident information is recorded and displayed inside the equipment together with the time when the accident occurred, or the status of each accident is communicated to the communication line. It can be counted and recorded at a specific place using it, and the direction of the accident occurrence is displayed on the spot or data is transmitted via a communication device and displayed at the place where people are present Yes,
Only by measuring the current, it is possible to locate the fault section of the transmission line of less than 30 km.

A sensor for detecting a current of the transmission line;
A three-phase synthesizing unit for synthesizing the respective current values of the three phases detected by the sensor; and a determination unit when the zero-phase current value obtained by the three-phase synthesizing unit exceeds a threshold value equal to or more than a certain value. A threshold processing unit for transmitting a signal; a phase difference calculation unit for comparing and calculating the phases of the previous zero-phase current value and the current value detected by the sensor; and a signal transmitted from the threshold processing unit. In the case where the phase difference calculation unit recognizes a phase that generates a phase difference of approximately 90 ° as a fault phase, and when the phase of the zero-phase current is advanced with respect to the fault phase current, on the load side, When the phase of the zero-phase current is delayed, the determination unit includes a storage unit that determines that the current is on the power supply side and stores a measurement content;
A ground fault section of an ungrounded overhead transmission line, comprising: a phase synthesizing unit, the threshold value processing unit, a power supply for supplying electricity for operating the phase difference calculating unit and the determining unit. It is a location device, the power source uses a solar cell and a storage battery connected via a control circuit for charging or supplying, and the data of the determination unit is recorded and displayed by a personal computer via a communication line, for example. In some cases, the location of the occurrence of the accident is displayed on the spot, and the location of the occurrence of the accident can be reliably grasped at the current detection point regardless of the relatively simple devices.

【Example】

The ungrounded three-phase overhead power transmission line has a schematic configuration as shown in FIG. That is, power supply 1
And three transmission lines 3 are connected between the
The transmission line constitutes the A phase, the B phase, and the C phase. At appropriate locations ZCT1 and ZCT2 of the overhead power transmission line, detection devices for detecting respective currents of the A phase, the B phase and the C phase as shown in FIG. 3 are installed. In this ungrounded three-phase overhead transmission line, when power is transmitted normally, the zero-phase current obtained by combining the currents flowing through the three phases A, B, and C is 0, and And its voltage is also 0
It is. That is, as shown in FIG. 2, the voltage V and the current A are represented by vectors in three directions.
This is because it is nothing but 0. Since the power factor is set to 0.9 or more, each current A normally has a delay of 25 ° or less with respect to each voltage V (because an inductive reactance exists in a power supply or a load).

When a ground fault occurs in the A-phase transmission line at the ground fault point 4, at that moment, the ground current Ig of the fault phase flows to the ground via the resistor Rg and the ground and the neutral point 5 Is applied with the voltage V0. From the relational expression of V0 = −Va / {1 + 3jw (C1 + C2) Rg}, it is possible to approximate Rg = 0 in the case of a complete ground fault, so that V0 = −Va. In FIG. 2, the voltage Va of the A-phase is grounded and the voltage becomes 0, and at the same time, the voltages Vba and Vca synthesized by the voltage V0, the voltage Vb, and the voltage Vc are generated. These voltages Vba and Vca
Are the voltages of the overhead transmission line at the time of the accident with respect to the B-phase and C-phase grounds, and form a capacitance C1 with the ground. Therefore, the currents Icc1 and Ibc1 flowing to the ground via the capacitance C1 are 90 °
To proceed, as shown in FIG. 2, the voltage Vba and the voltage Vca are drawn so as to be counterclockwise at right angles. And
The voltages Vba and Vca plotted at right angles to the capacitance currents Icc1 and Ibc1 counterclockwise from the ground current Ig in the fault phase, respectively.
Are synthesized. Measurement points ZCT1 and ZCT2
Is the sum of the zero-phase currents I01 and I02 at the fault phase ground current Ig. The zero-phase current I01 has a phase lead of approximately 90 ° with respect to the fault phase current Ia due to the presence of the capacitance C. However, since the zero-phase current I02 is reversed,
A phenomenon occurs as if the phase delay of the fault phase current Ia is substantially 90 °.

The present invention seeks to determine the ground fault point by grasping such a phenomenon. FIG.
This shows the outline of two cross beams 1 on two electric poles 11.
2, 16 are fixed. In the cross beam 16, the insulator 17,
The A-phase, B-phase, and C-phase wires 19 are locked via 18, and the jumpers 20 are electrically connected to the wires 19 of each phase so as to sandwich the insulators 17, 18. Further, the current detector 25 is fixed to the cross beam 12 and includes the insulator 13 and a sensor 14 provided at an upper end thereof.
The jumper wire 20 passes through the sensor 14 and the sensor 1
4 measures the current of the jumper wire 20. As shown in FIG. 4, the sensor 14 of the current detector 24 has a ferrite core 32 surrounding a power line 31 and a photomagnetic field sensor 33 utilizing the Faraday effect partially inserted. The optical magnetic field sensor 33 converts the magnetic force detected by the ferrite core 32 in proportion to the current of the power line 31 into light.
4, and transmits the light of the optical magnetic field sensor 33 to the detection device 22 shown in FIG. The detecting device 22 further includes a solar cell 21 which is a solar cell and a battery 23 which is a storage battery, and supplies electricity to each component of the detecting device 22 so that it can be detected all the time.

The detecting device 22 further includes a signal processing device as shown in FIG.
And the current values IA, IB and I converted from light to electricity
C is converted into a so-called zero-phase current I0 and its phase φ by a three-phase synthesizer 41.
I0 is synthesized. Further, the current values IA, IB and I
C is converted into current values Ia, Ib and Ic of respective phases whose levels are matched with the zero-phase current I0 via the level converter 43 and transmitted to the phase difference calculator 44. This is the zero-phase current I
This is because the current value IA, IB, and IC of each phase is several tens of amperes or more, whereas 0 is about several amperes at most, and it is impossible to compare them as they are. Thus, the zero-phase current I
0 is a threshold value processing unit 4 that transmits to the determination unit 45 so as to recognize that a so-called accident has occurred when the current is a certain value or more.
2 and input to the phase difference calculator 44, where the current values Ia, Ib and Ic of each phase and the phase difference are calculated, and the phase current that produces a phase difference of approximately 90 ° with the zero-phase current I0 is divided. However, the accident phase is specified and input to the determination unit 45. The determination unit 45 includes a storage unit having a storage function. If the specified fault phase is the A phase, the zero-phase current I0 input from the threshold value processing unit 42 advances by about 90 ° from the fault current Ia. When you are
It is determined by the detection device 22 to be on the load side, and when it is almost 90 ° delayed, it is determined to be on the power side. Then, the determination result is transmitted to the so-called accident center via the communication line by the modem 46, and the accident situation is recorded. In some cases, the direction of occurrence of the accident may be displayed on the display unit 49 on the spot. The detection device 22 includes a power supply unit for supplying electricity, and the power supply unit includes the solar cell 2.
1, a battery 23, and a switching device 47.
In accordance with the power generation status, the power is supplied to each part of the detection device via the wiring 48 and the battery 23 is appropriately charged.

FIG. 6 schematically shows the orientation method when a sensor is installed at one point on the transmission line. The current sensor at the measurement point S1 is installed on each of the three-phase transmission lines as described above. And the zero-sequence current I0 is the
Is determined to be about 90 ° behind the fault point F1, it is determined that the fault point F1 is closer to the power supply than the measurement point S1, and the zero-phase current I0 is determined to be about 90 ° ahead of the ground fault fault phase current If. In this case, it is determined that the fault point F1 is on the load side from the measurement point S1, so that it is possible to instantaneously specify the location of the fault and the inspection range of the transmission line. FIG. 7 schematically shows the orientation method when sensors are installed at two points on the transmission line. As described above, the current sensors at the measurement points S1 and S2 have the three-phase transmission lines as described above. If it is determined that both the zero-phase current I0 and the ground-fault fault phase current If are delayed by about 90 °, the fault point F
1 is on the power supply side from the measurement point S1, and the zero-phase current I0
, It is determined that the fault point F3 is on the load side of the measurement point S2 when both of the ground fault phase current If advance by about 90 degrees. Further, it is determined that the zero-phase current I0 at the measurement point S1 leads the ground-fault fault phase current If by about 90 °, and the zero-phase current I0 at the fault point F2 becomes zero.
If it is determined that both are about 90 ° behind f, the fault point F2 is determined to be between the measurement points S1 and S2.
It is possible to instantaneously identify the location of the accident and the inspection range of the transmission line.

In the present invention, the following fault locating is possible by utilizing the fault information of a substation or the like. That is, as shown in FIG.
When the zero-phase current value is plotted on the vertical axis, it is recognized that the zero-phase current value changes proportionally in the horizontal axis direction. In the sensor S2 installed near the center of the transmission line, the zero-phase current values match, and the above-described phase determination is indispensable. However, the sensor S1 or S3 shifted from the vicinity of the center toward the end has two sensors. Zero-sequence currents, namely IOS1 and IOS1 'and IOS3 and IOS3', are generated. Now, as shown in FIG.
If the threshold value in FIG. 2 (FIG. 5) is smaller than the zero-phase currents I0S1 and I0S3 and larger than the zero-phase currents I0S1 'and I0S3', the fault F1 or F4 is detected. Is not detected. In other words, if the threshold is exceeded, the accident is on the side where the distance between the sensor installation location and the end is short, and if the threshold is not exceeded, the distance between the sensor installation location and the end is long. Will have an accident.

Further, by utilizing accident information on substations and the like, the following accident localization is possible. As described above with reference to FIG. 1, when a ground fault occurs in the A-phase transmission line at the ground fault point 4, at that moment, the ground current Ig of the fault phase flows to the ground via the resistor Rg, and the ground and the neutral The voltage V0 is applied to the point 5. From the relational expression of V0 = −Va / {1 + 3jw (C1 + C2) Rg}, it can be approximated to Rg = 0 for a complete ground fault, but if the ground fault is not complete, Rg =
Cannot be approximated to 0. Zero-phase voltage V0 of ground fault in this case
Depends on the resistance Rg, and as Rg increases, V0 decreases. However, the value of the voltage V0 determined by the resistance Rg at the time of the ground fault is not affected by the location of the ground fault, and the entire area of the transmission line is Shows a constant value over the range. On the other hand,
The zero-phase current I0 at the time of the ground fault also depends on the resistance Rg.
It is also affected by the location of the ground fault. As a result,
When the resistance Rg is large, the zero-phase current I0 at the measurement point naturally becomes small. However, V0 / V0max (Rg = 0) and I0 /
When the value is compared with I0max (Rg = 0), as shown in FIG. 10, they are almost the same regardless of the value of the resistance Rg at various ground fault points. Fig. 10 shows the measurement results of the zero-phase current I0 at 20 km from the substation when a ground fault occurs at a location 25 km away from the substation in a model with a transmission line length of 30 km. It can be seen that when the resistance Rg of the ground fault exceeds 1 kΩ, the value sharply decreases, but the two values of the voltage and the current are almost the same.

Therefore, in the block diagram of FIG.
By setting, as a trigger value, a current of, for example, about 0.25 to 0.4 A, which is smaller than the threshold value and slightly larger than the noise current, the detection function can be performed. An accident has occurred by detecting a large V0.
⇒ Judge that the accident point has occurred at the measurement point and on the long side of the transmission line. 2) When no trigger occurs For example, even if V0 is detected at a substation, if the range of V0 is relatively small and within the range of noise, it may be unclear whether an accident has occurred. ⇒ In this case, it is determined that “location is impossible” (because it exceeds the range of the discriminating ability of the device, and in FIG. 5, an accident in which the trigger value of the discriminating unit 45 is not detected is displayed). As described above, the present invention estimates the zero-phase current to be detected by the current sensor installed on the transmission line based on the zero-sequence voltage in the case where the ungrounded transmission line has an accident. Sometimes by comparing with the zero-phase current obtained by the current sensor,
This is a method for locating the ground fault section of an ungrounded overhead transmission line that can estimate the direction in which an accident has occurred.Also, based on the zero-phase voltage detected at the time of the accident,
Two types of current are estimated for the case where an accident occurs on the longer line and the case where an accident occurs on the shorter line, and depending on which one of the currents detected at the time of the accident is closer,
A method for locating a ground fault section of an ungrounded overhead transmission line characterized by estimating the direction in which an accident has occurred. If the estimated two types of zero-phase current values are close to the larger one, the transmission line path is short. 3. The ground fault accident locating of an ungrounded overhead transmission line according to claim 2, wherein it is determined that an accident has occurred on the side of the transmission line, and if the distance is close to the smaller one, it is determined that the accident has occurred on the longer transmission line side. Is the way.

Further, in the case where the zero-phase current cannot be detected because the current sensor device installed in the middle of the transmission line is below the trigger level despite the accident in the ungrounded transmission line, If it is estimated that the zero-phase current is estimated to be greater than the trigger level when it is assumed that an accident has occurred on the short side of the overhead transmission line, it is determined that an accident has occurred on the long side of the line, When the estimated current value is equal to or less than a trigger level, the method is a method for locating an ungrounded overhead transmission line to a ground fault accident section. At the current detection point of the ungrounded three-phase overhead transmission line,
When there is an accident in the overhead transmission line, when the zero-phase current to be detected does not reach a fixed trigger value smaller than the threshold value and, for example, V0 / V0max (Rg = 0) ≧ 50%, It is determined that an accident has occurred on the side where the distance between the current detection point and the end of the overhead transmission line is long, and V0 / V0max (Rg =
0) When <50%, it can be determined that the orientation is impossible. However, in this case, V0max is the zero-phase voltage when the ground fault resistance Rg = 0, and V0 is the zero-phase voltage at the time of the ground fault. Thus, if information about the occurrence of an accident is obtained via an NTT line or the like at a substation or the like having a circuit breaker for maintenance, the accident can be located.

[0019]

As described above, the current sensors are directly installed in each phase of the transmission line, and whether the zero-phase current at the time of an accident is delayed or advanced as compared with the current phase of the accident phase is determined. By detecting, it is possible to determine whether the accident location is on the power supply side or load side from the sensor installation point,
When the current sensors are installed at two locations on the transmission line, it is possible to use the accident information of a substation or the like to determine whether or not there is between both sensor points and the end of the line. Even when the trigger value, which is a constant current value after the accident flowing through the transmission line, is not detected, if the zero-phase current at that time is large based on the zero-sequence voltage at the time of the accident at the substation, the sensor It is necessary to narrow down the scope of the accident assuming that an accident has occurred on the longer side of the transmission line from the installation location, and to compare it with the zero-phase current expected at the sensor ground even when the zero-sequence voltage at the time of the accident is small. If the orientation is not possible, it is treated as non-orientable, thereby expanding the orientation range. Moreover,
Detecting the occurrence of an accident by detecting the case where the current value after the accident flowing in the transmission line exceeds a certain threshold or more, comparing the phase of the current value after the accident and the phase of the zero-phase current value If the phase at the current detection point is delayed,
Also, when the phase is advanced, an accident is displayed on the load side, so that the range of occurrence of the accident can be narrowed around the installation location of the sensor and the situation for each accident is displayed, Even if the length of the transmission line is less than 30 km and more than 10 km, the scope of the accident that occurred in a short time can be assumed.

Further, the fault section locating apparatus for an overhead transmission line according to the present invention includes a sensor for detecting a current of the transmission line, a three-phase synthesizing means for synthesizing respective current values of the three phases detected by the sensor, Threshold value processing means for transmitting a signal to the determination unit when the zero-phase current value obtained by the three-phase synthesizing means exceeds a threshold value equal to or more than a predetermined value; A phase difference calculating section for comparing and calculating the phase with the current value, and a phase which generates a phase difference of about 90 ° in the phase difference calculating section when receiving a signal transmitted from the threshold value processing means. A determination unit that recognizes a phase and determines that the current is on the load side when the zero-phase current value is advanced with respect to the fault phase current, and that it is on the power supply side when the zero-phase current value is delayed. , The three-phase combining means, the threshold And a power supply that supplies electricity for operating the phase difference calculation unit and the determination unit. Since the solar cell and the storage battery connected via a control circuit that performs charging or supply, and the data of the determination unit is recorded by a communication line,
With relatively simple equipment and a reliable transmission line with a length of less than 30 km and a length of 10 km or more, it is possible to perform ground fault section identification for ungrounded overhead transmission lines.

[Brief description of the drawings]

FIG. 1 is a conceptual diagram schematically showing an ungrounded three-phase overhead power transmission line.

FIG. 2 is a vector diagram of voltage and current at the time of an accident in an ungrounded three-phase overhead power transmission line.

FIG. 3 is a schematic diagram of a detection device of the present invention.

FIG. 4 is a schematic diagram of a detection portion in the detection device of the present invention.

FIG. 5 is a block diagram of signal processing in the detection device of the present invention.

FIG. 6 is an orientation method in a case where a sensor is installed at one location on a transmission line.

FIG. 7 is an orientation method when sensors are installed at two locations on a transmission line.

FIG. 8 is a change diagram of a zero-phase current value at the time of an accident in a transmission line.

FIG. 9 is a change diagram of a zero-phase current value of a transmission line detected by the detection device of the present invention.

FIG. 10 is a graph showing a decrease rate of a zero-phase voltage and a zero-phase current with respect to a maximum value with respect to a ground fault resistance.

FIG. 11 is a schematic diagram of a conventional technique for a method for locating an accident section of an overhead line.

FIG. 12 is another schematic diagram of the related art regarding a method of locating an accident section of an overhead line.

[Explanation of symbols]

 1: Power source 2: Load 3, 61: Transmission line 4: Ground fault point 5: Neutral point 12, 16: Cross beam 14: Sensor 19: Electric wire 20: Jumper wire 21: Solar cell 22: Detector 23: Battery 24: Optical cable 25: Current detection unit 31: Power line 32: Ferrite core 33: Optical magnetic field sensor 35: Optical fiber 41: Three-phase synthesis unit 42: Threshold processing unit 43: Level conversion unit 44: Phase difference calculation unit 45: Judgment unit 46 : Modem 47: Switch 48: Wiring 49: Display 62A, 62B: Detector 63: Central device 64: Power supply 65: Load 70: Overhead transmission line 73: Voltage sensor 80: Underground transmission line 81: Current sensor 90: Identification device

Continuation of front page (72) Inventor Kazuhiro Hosono 1-2-2 Odori Higashi, Chuo-ku, Sapporo, Hokkaido Inside Hokkaido Electric Power Company

Claims (13)

[Claims] 1. A zero-phase current to be detected by a current sensor installed on an overhead transmission line based on a zero-phase voltage when an accident occurs on an ungrounded overhead transmission line. A method for locating a ground fault of an ungrounded overhead transmission line, comprising estimating a direction in which an accident has occurred by comparing the zero-phase current obtained by the current sensor. 2. Based on a zero-phase voltage detected at the time of an accident of an ungrounded overhead transmission line, an accident occurs on a longer line and an accident occurs on a shorter line at a sensor installation location. A method for estimating a ground fault section of an ungrounded overhead transmission line, comprising estimating two types of currents in the case of occurrence and estimating an accident occurrence direction based on which of the currents detected at the time of the accident is closer. 3. When the estimated two types of zero-phase current values are close to the larger one, it is determined that an accident has occurred on the short transmission line side. The method for locating a ground fault section of an ungrounded overhead transmission line according to claim 2, wherein it is determined that an accident has occurred on the track side. 4. In a case where a zero-phase current cannot be detected because a current sensor installed on the overhead transmission line is below its trigger level, despite an accident in an ungrounded overhead transmission line, If it is estimated that the zero-phase current is estimated to be greater than the trigger level when it is assumed that an accident has occurred on the short side of the overhead transmission line, it is determined that an accident has occurred on the long side of the line, A method of locating a ground fault section of an ungrounded overhead transmission line, wherein the locating is disabled when the estimated current value is equal to or lower than a trigger level. 5. When a zero-phase current exceeding a predetermined threshold value is detected when an accident occurs in an ungrounded three-phase overhead transmission line, a current detection portion attached to the overhead transmission line and the overhead When it is determined that an accident has occurred on the side where the distance to the end of the transmission line is short and a zero-phase current exceeding the predetermined threshold is not detected, the current detection point and the end of the overhead transmission line are not detected. A method for locating a ground fault section of an ungrounded overhead transmission line, comprising determining that an accident has occurred on a side having a long distance to a section. 6. The ungrounded overhead transmission line according to claim 5, wherein the threshold value is a set value between two types of zero-phase current detected at a current detection point of the ungrounded three-phase overhead transmission line. Ground fault accident section location method. 7. At the current detection point of an ungrounded three-phase overhead power transmission line, a phase of a current which causes a phase shift of approximately 90 ° with a phase of a zero-phase current exceeding a predetermined threshold value in an accident is recognized as an accident phase. When the phase of the zero-phase current is ahead of the phase of the current in the fault phase, it is determined that the fault has occurred on the load side, and when the phase of the zero-phase current is late, the fault has occurred on the power supply side. A method of locating a ground fault accident section of an ungrounded overhead transmission line, characterized by the following. 8. The ungrounded overhead transmission line ground according to claim 7, wherein the phase shift of approximately 90 ° from the phase of the zero-phase current is a phase difference α between the voltage and the current determined by 90 ° ± power factor. How to locate the accident accident section. 9. The method according to claim 7, wherein the status of the determination unit is recorded via a communication line. 10. A sensor for detecting a current of a transmission line and a current value of each of three phases detected by the sensor.
A phase synthesizing unit; a threshold processing unit for transmitting a signal to a determination unit when a zero-phase current value obtained by the three-phase synthesizing unit exceeds a threshold value equal to or greater than a predetermined value; And a phase difference calculator for comparing and calculating the phase of the current value detected by the sensor. When the signal transmitted from the threshold processing unit is received, the phase difference calculator is substantially 90 ° apart. It recognizes the phase that causes the phase difference as the fault phase and is on the load side when the zero-phase current value is advanced with respect to the fault phase current, and on the power supply side when the zero-phase current value is late. And a power supply for supplying electricity for operating the three-phase synthesizing unit, the threshold value processing unit, the phase difference calculating unit, and the judging unit. Ground fault accident location system for system overhead transmission lines. 11. A power supply is a solar battery and a storage battery connected via a control circuit for charging or supplying.
3. The ground fault accident section locating device for an ungrounded overhead transmission line according to 4.). 12. The apparatus for locating a ground fault section of an ungrounded overhead transmission line according to claim 10, wherein the judging unit transmits or receives and records data through a communication line. 13. The ground fault section locating apparatus for an ungrounded overhead transmission line according to claim 10, wherein the data of the judging section displays the direction of the accident on the spot on the display section.