JPH04190642A - System for judging fault section of transmission line - Google Patents

Abstract

PURPOSE:To judge a fault in a bushing part as a fault on the underground line side correctly, by mounting optical CTs on voltage applied parts of the overhead line side and mounting a voltage sensor on the underground line side, and by judging the direction of a fault point through the output signals of the CTs and the sensor when the fault is generated. CONSTITUTION:On voltage applied parts of the side of overhead lines 2 above bushings 5, optical CTs 6 are mounted, and the currents of the conductors of the respective phase on the side of the overhead liens 2 can be sensed. That is, the light signals taken out from the optical CTs 6 of the respective phases are converted to electrical signals by optical sensors 8, and thereafter, the signals are combined by a zero-phase combiner 9. As a result, usually the respective phase currents are canceled by each other, and the output of the zero-phase combiner 9 after combining becomes zero. However, when a fault is generated in one of phases, the balance among the three phases is lost, and since the output of the zero-phase combiner 9 is not zero, this output level is sensed by a level sensor 10. Also, on the underground lines 3 side, a voltage sensor 11 is mounted, and by the phase differences between the sensed voltage and the currents sensed by the optical CTs 6, the direction of a fault current can be judged too.

Description

Detailed Description of the Invention (Industrial Field of Application) The present invention provides a method for determining whether a fault point is on the overhead line side or underground when a ground fault occurs in a power transmission line where an overhead line and an underground line are connected. The present invention relates to a power transmission line failure section determination system that makes it possible to easily determine from a remote location whether the transmission line is on the track side or not.

(Prior art) When a ground fault occurs on a power transmission line that connects an overhead line and an underground line and a circuit breaker is activated, if a fault occurs on the underground line side, the underground cable is Since it is thought that dielectric breakdown has occurred, there is a risk that the accident will escalate if the power is turned on again.

On the other hand, if a failure occurs on the overhead line side, it is necessary to immediately turn on the power again to restore the power outage as soon as possible.

Therefore, there is a need for a system that can immediately determine at a remote monitoring station whether the accident section is on the underground track side or the overhead track side.

However, in the conventional system, the current sensor was installed on the underground line side of the bushing provided at the connection between the two, so if a failure occurred inside the bushing at the connection, the current sensor was installed on the overhead line rather than the current sensor. It is determined that an accident occurred on the side. For this reason, an accident inside the bushing would be mistakenly recognized as an accident on the overhead line, and the power would be immediately turned on again, potentially exacerbating the accident.

(Problems to be Solved by the Invention) As described above, the present invention makes it possible to correctly determine a failure in the bushing part, which was a blind spot in the conventional failure section discrimination system, as a failure on the underground line side, and thereby It was completed with the aim of providing a faulty section determination system for power transmission lines that can prevent the spread of bushing accidents due to reinsertion.

(Means for Solving the Problems) The present invention, which has been made to solve the above problems, provides a power supply section on the overhead line side of the part where the power transmission line is connected from the overhead line to the underground line via the bushing. The system is characterized in that a CT is installed and a voltage sensor is installed on the underground line side, and the direction of the failure point when a failure occurs is determined based on these output signals.

The present invention will be explained in more detail below with reference to illustrated embodiments.

(Example) Figure 1 is a diagram conceptually showing the entire power transmission line.
) is the power supply, (2) is the overhead line, (3) is the underground line, (4
) is a load, and a bushing (5) is provided at the connection between the overhead line (2) and the underground line (3).

Fig. 2 shows the main part of the fault section determination system of the present invention. Optical CT (61 converts the strength of the magnetic field generated by the current flowing through the conductor of the charged part into an optical signal using a Faraday element such as a BSO, and transmits the signal to a photodetector (8) through an optical fiber (7). It is possible to detect the current in the conductor of each phase on the overhead line (2) side.In the embodiment, the optical CT (6) is supported on the upper end of the insulator (8) with a built-in optical fiber. The optical fiber (7) passes through the inside of the insulator and is led out to the ground side.The optical signals extracted from the optical CT (6) of each phase are converted into electrical signals by the photodetector (8). Then, the zero phases are combined in the zero phase combiner (9).As a result, under normal conditions, the currents of each phase cancel each other out and the output after zero phase combination becomes zero, but if a fault occurs in one of the phases. Then, the balance of the three phases collapses,
Since the output from the zero-phase synthesizer (9) is not zero, its level is detected by the level detector QOI. In this way, the occurrence of an accident can be detected by the optical CT (6) on the overhead line (2) side.

Further, a voltage sensor aυ is attached to the underground line (3) side. The output is sent to the above-mentioned optical CT (6
) is displayed on the display section α3 together with the output from the 3rd party, and is transmitted to a remote monitoring station or the like by a known communication means.

(Function) In the power transmission line failure section determination system of the present invention configured as described above, even when a ground fault occurs in the underground line (3), it is possible to detect that a ground fault has occurred inside the bushing (5). Occasionally, a fault current flows through the overhead line (2) and optical CT
(6) is detected. In contrast, the overhead line (2
) when a ground fault occurs, optical CT (6)
does not detect current. Therefore, according to the present invention, the overhead line (
It goes without saying that it is possible to accurately determine whether an accident on the 2) side is an accident on the underground line (3) side, and if a ground fault occurs inside the bushing (5), the power can be turned on again. The accident is determined to have occurred on the underground track (3) side, where there was no accident.

Therefore, when a ground fault occurs inside the bushing (5), there is no need to turn on the power again because the ground fault occurs on the overhead line (2) side, thereby preventing the accident from spreading.

In addition, in the present invention, the voltage sensor 0 is installed on the underground line (3) side.
Since υ is attached, the direction in which the fault current flows can be determined based on the phase difference between current and voltage. Even in the case where the fault current flows from the load side toward the fault point in 2), the fault section is connected to the overhead line (2).
) side or the underground track (3) side can be accurately determined. Note that the voltage sensor aυ is provided on the underground line (3) side because it is easy to insulate and install, and the equipment cost can be reduced.

(Effects of the Invention) As explained above, the present invention is capable of correctly distinguishing a ground fault inside a bushing, which was a blind spot in the conventional failure section discrimination system, from an accident on the underground line side. This makes it possible to prevent an accident inside the bushing from being erroneously determined as an accident on the overhead line and turning the power back on, which would aggravate the accident, as was the case in the past. In addition, in the present invention, since the voltage sensor is installed on the underground line side,
The direction of the fault current can be correctly determined based on the phase difference between the current detected by optical CT and the voltage detected by the voltage sensor, and the equipment as a whole is simpler than when the voltage sensor is also installed on the overhead line side. Cost can be reduced. Therefore, the present invention greatly contributes to the development of industry as a power transmission line failure section determination system that eliminates the problems of the conventional system.

[Brief explanation of drawings]

FIG. 1 is a system diagram conceptually showing the entire power transmission line, and FIG. 2 is a block diagram showing the main parts of an embodiment of the present invention. (2): Overhead line, (3): Underground line, (5): Bushing, (6): Optical CT, αυ: Voltage sensor. Patent applicant: Nippon Insulator Co., Ltd. Representative name: Akira Shima Buma
Watanuki Tatsu Separation
Fumi Yamamoto page 11

Claims (1)

[Claims] An optical CT is installed on the power charging section on the overhead line side where the power transmission line is connected to the underground line via a bushing, and a voltage sensor is installed on the underground line side, and these output signals cause failures. A power transmission line failure section determination system that determines the direction of a failure point when a failure occurs.