JPH06289067A - Current detector for fault point locator - Google Patents

Abstract

PURPOSE:To transmit information of surge occurring timing (first wave of a surge current) and a commercial frequency component (amplitude and phase) by one LED in a fault current detector for a fault detecting apparatus of a transmission line. CONSTITUTION:A high-pass filter 3 and a low-pass filter 4 are respectively connected to the output terminals of two wound-core CTs or a wound-core CT having two windings wound on the same core, a full-wave rectifier 5 is connected to the output side of the filter 3, a half-wave rectifier 6 is connected to the filter 4, the polarities of the outputs of both the rectifiers are matched and an LED 7 is connected.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a current detection circuit used in a device for locating an accident point when an accident occurs in an underground power transmission line.

[0002]

2. Description of the Related Art As an accident point locating device in the case of a ground fault of an ultrahigh voltage underground power line, for example, the 1992 National Congress of the Institute of Electrical Engineers of Japan
As stated in No. 1445 "Development of surge current receiving type fault locator for ultra high voltage underground power transmission line", it is a sensor that arranges the first surge current wave at two locations on the line at the time of an accident. There is a method of detecting and locating the fault point by measuring the arrival time difference of the detected surge current. In this method, a Faraday element that changes the intensity of light with a magnetic field generated by the current is used to detect the surge current. FIG. 3 shows the device in a block diagram. Transmission line 20 is a pipe type 3-core OF
In this line, sensors 21 and 21 'having a Faraday element 22 interposed in an air gap of an annular ferrite core are installed so as to surround a three-core cable at a predetermined distance L in this line. . The surge current generated at the accident point F is detected by the sensors 21 and 21 ′ after the time of t ₁ and t ₂ . Slave station located at sensor 21 due to the first surge current wave reaching sensor 21 located near accident point F
After the counter starts operating in LS1 and the sensor 21 'detects the first surge current wave, a pulse for stopping the counter is transmitted from the slave station LS2 to the slave station LS1. Slave station LS at this time
The count time t _{m at} 1 is represented by the following equation (1). t _m = t ₂ + t ₃ −t ₁ (1) where t ₁ : detection time of surge current in sensor 21 t ₂ : detection time of surge current in sensor 21 ′ t ₃ : from sensor 21 ′ to slave station LS1 Pulse arrival time for stopping the counter The transmission time difference t to the sensors 21 and 21 'is expressed by the following equation (2). t = t ₂ −t ₁ = t _m −t ₃ (2) Orientation distance: If X, X = (L−v.t) / 2 (3) v: Surge speed Transmission time of counter stop pulse here t ₃ is irrelevant to the location of the accident point and may be obtained in advance. The obtained time t and the distance X from the surge propagation velocity v in the cable, which is obtained in advance, to the accident point are obtained by (3).
The surge detection information and counter value are from the slave station LS1 to the master station MS.
And the distance is converted by the CPU inside the master station,
Is displayed.

On the other hand, as a device for detecting an electric current, it is shown not in a Faraday element but in a "electric quantity measuring instrument using light"("ElectricalCalculation" reprint, June 1985 issue, Vol. 53, No. 9). As described above, there is an example of a combination of CT and E / O (LED), and the lightning current of the tower is measured.

[0004]

As described above, the Faraday element is used as the current detecting element in the accident locator, but it is necessary to keep the LED lit at all times.
High power consumption. This is the CT and E / O (LED)
Although the same function can be obtained by substituting the combination of No. 1 and No. 2, there is a drawback that the LED emits light only in one polarity and cannot be detected when a fault current of opposite polarity flows. The present invention detects this regardless of whether the polarity of the surge current is positive or negative. In addition, since the polarity of this fault current is an important factor for knowing the fault zone, the present invention therefore , It is intended to obtain information on the surge intrusion timing and the current polarity (phase) with only one side polarity.

[0005]

According to the present invention, two CTs are used, or two sets of windings are provided on the same CT core, and one output terminal thereof is provided with a high-pass filter for passing a surge current, and the other is provided with a commercial frequency. A low-pass filter that passes The output after passing through the high-pass filter passes through the double-wave rectifier and guides the output of the same polarity to the LED regardless of the positive / negative polarity of the surge current. The output after passing through the low-pass filter passes through the half-wave rectifier and is led to the same LED. By adopting such a configuration, even if the polarity of the surge current generated at the accident point is positive or negative,
It can be detected by ED. Therefore, such a surge current detection circuit can be installed at each of the sensor positions of the accident point locating device as described in FIG. 3 to locate the accident point.

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the embodiment shown in FIG. 1 and the operation waveform chart of each part of the circuit shown in FIG. A magnetic core (not shown) of a wound type CT is arranged so as to surround the three-core underground power transmission line 1, and the output terminal of the secondary winding 2 of this CT is connected to the high-pass filter 3. Further, the output terminal of the secondary winding 2 ′ wound around the same magnetic core or the CT coupled separately from the CT is connected to the low pass filter 4. The high-pass filter 3 has a performance of passing a surge current and blocking a commercial frequency, and the low-pass filter 4 has a performance of blocking a surge current and passing a commercial frequency. The output side of the high-pass filter 3 is connected to the double-wave rectifier 5, the output side of the low-pass filter 4 is connected to the half-wave rectifier 6, and the output sides of the both rectifiers 5 and 6 are aligned in parallel between the terminals of the LED 7. Connected. An optical fiber 8 is coupled to the light emitted from the LED 7, and the other end of the optical fiber 8 extends to the slave station LS1 and / or LS2 in FIG.

[0007]

[Operation] As shown in the waveform diagram of FIG. 2, when an accident occurs on the power transmission line, a surge current propagates on the line from this accident point. The fault current signal If can be captured by CT. This current signal If has similar waveforms If1 and If2 at the output terminals of the secondary windings 2 and 2 '. The output S1 of the high-pass filter 3 has a waveform in which only the surge component at the initial stage of the accident remains, and by passing this waveform through the double-wave rectifier circuit 5, it is replaced with the surge component on the positive side only. On the other hand, the fault current If2 from the secondary winding 2'is removed by the low-pass filter 4 from the output S2, and the initial surge component is removed. Only the commercial frequency component remains, and the fault current If2 is further passed through the half-wave rectifier 6. It becomes a half wave in which only the positive component remains. Since both of the both-wave rectifier output and the half-wave rectifier output are added to the LED 7 in parallel, the light emission output S0 of the LED 7 has only one LED at the timing of surge generation (surge current first
Information on the ripples and commercial frequency components (magnitude and phase) can be transmitted. If the surge current detection circuit described above is installed at each of the sensor positions of the orientation device shown in FIG. 3, it is possible to locate the accident point. The present invention can also be applied to detection of fault location in a distribution line. Also,
Although the surge current detection circuit is installed at two locations in the above embodiment,
A plurality of detection circuits are installed at an appropriate distance.

The surge current detection circuit as described above is arranged at the positions of the slave stations LS1 and LS2 in FIG. 3, one accident detection section is provided between the slave stations, and there are power sources on both sides of this detection section. Fig. 4 and Fig. 5 show the current waveforms and optical output waveforms captured by each surge current detection circuit when the fault point is inside the section and when the fault point is outside the section. , The surge current flowing through both circuits and the commercial frequency current waveform following it have opposite polarities, and the commercial frequency rectified component is half-wave rectified, so the timing of this output is shifted by half wave. . On the other hand, when the accident point is outside the section, half-wave rectification of the commercial frequency occurs in both surge current detection circuits in the same pole and the same phase. Although not described in detail here, by comparing the half-wave waveform positions of both surge current detection circuits,
It is possible to determine whether the accident point occurred inside the section or outside the section. When the current is a one-sided power supply and the fault point is within the section, one surge current detection circuit may not generate commercial frequency current following the surge current. It is possible to determine that the accident point has occurred within the section due to the occurrence of the above. However, these are also one of the characteristics obtained by using the surge current detection circuit of the present invention.

[0009]

According to the present invention, the rise of the first wave can be detected regardless of whether the surge current has positive or negative polarity, and the surge current detection circuits provided at a plurality of points can be used to measure the difference in the surge current arrival times. It will be possible. Further, since the commercial frequency component is also detected, it is possible to determine the accident occurrence section by comparing the levels or phases detected by the adjacent current detection circuits. Furthermore, this surge current detection circuit does not constantly emit light from the LED
Since the light is emitted, the power consumption of the accident locator can be reduced.

[Brief description of drawings]

FIG. 1 shows an embodiment of the present invention.

FIG. 2 shows waveforms at various points in the embodiment of FIG.

FIG. 3 shows a conventional transmission line accident locator.

FIG. 4 shows a waveform diagram when the accident point is within the section.

FIG. 5 shows a waveform diagram when the accident point is outside the section.

[Explanation of symbols]

 1 Underground transmission line 2, 2'CT secondary winding 3 High pass filter 4 Low pass filter 5 Double wave rectifier 6 Half wave rectifier 7 LED 8 Optical fiber

Claims (1)

[Claims] 1. An accident point is provided by arranging current detection units at a plurality of locations on the same transmission / distribution line to detect surge currents at the time of a ground fault and by detecting a time difference between surge currents reaching adjacent current detection units. Is a current detection circuit used as the current detection unit in a fault locator for locating a distance to, and is a two-winding type CT or a winding type C in which two sets of windings are formed on the same magnetic core.
A high-pass filter and a low-pass filter are connected to the output terminals of T, a double-wave rectifier is connected to the output side of the high-pass filter, and a half-wave rectifier is connected to the output side of the low-pass filter. A current detection circuit for an accident locator, characterized in that the light emission of the LED is coupled to an optical fiber.