JPH02212778A - Detecting method for disconnection of optical fiber for use in transmission of detecting signal of earthing accident of transmission line buried in ground - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION FIELD OF INDUSTRIAL APPLICATION 1 The present invention relates to a method for detecting a break in an optical fiber for transmitting a signal to detect a ground fault in an underground transmission line such as a power cable.

Shijoto technology] 11+! Are you good at power transmission lines? In order to quickly detect the location of a ground fault, underground power transmission lines are divided into several sections and the fault is detected in which section.

As a means of this, for example, zero-phase current transformers are placed at predetermined intervals on a power transmission line, and the ground fault current that occurs due to a ground fault on the power transmission line is directly converted into electro-optical light, which is proportional to the ground fault current. A device that emits light with high intensity, sends the dirt to a substation, etc. via an optical fiber cable, and detects the location of the 1F fault at the substation, etc.
The steps are known.

[Problem to be solved by the invention]

This method uses optical fiber cables for transmission to substations, and since optical fiber cables are insulating materials, even if surges occur on the transmission line, there will be no risk of circuit burnout, etc. It is excellent in that it does not cause any problems and utilizes the advantage of not being affected by electrical conductivity and 1 m conduction.

However, since the ground fault does not exist in reduction C, it is unclear whether the optical fiber/, "-full is turned off or not, so when the ground fault occurs at 71.
In view of the current situation, the present invention aims to solve the problem of zero-phase power generated by a ground fault in an underground power transmission line. An optical signal proportional to the ground fault current from the current transformer and a light for disconnection detection from the receiving end 4i"+"J-
An underground transmission system characterized by optically coupling and transmitting the light to the receiving end via an optical fiber, converting the transmitted light into an electrical signal to detect ground fault current, and detecting the presence or absence of a break in the optical fiber. This is a method for detecting disconnection of an optical fiber for transmitting a detection signal due to ground fault 11 in an electric wire.

(Effect 1) In the present invention, the optical signal for disconnection detection from the receiving end is converted into an optical signal proportional to the ground fault current from the zero-phase current transformer that occurs due to a ground fault in an underground power transmission line. Since the signal is optically coupled and transmitted to the receiving end of a substation or the like via an optical fiber, it is possible to constantly detect whether or not the optical fiber has been cut.

In addition, since the transmitter uses the ground fault current as the power source for the device, there is no need for a power supply to detect the ground fault current. .

・Since the optical signal comes from the light source, there is no need for a power source to detect the presence or absence of disconnection of the light, )γ・i/\! 9,
For this reason, the installation location of the feeder is not subject to control) +1
There is one point.

[Example] Hereinafter, the present invention will be explained according to the illustrated example.

In the figure, l is a zero-sequence current transformer installed at a predetermined interval on an underground line (three-phase power transmission/distribution line). If a ground fault occurs in a part of the tIi line, the output will be affected and the current on the secondary side Q, ″, 2A of a 9-phase current transformer will be lh. The phase current transformer 1 is used to measure the current that is insulated from the line. It is a VI through type with side windings.

This extracted zero-sequence ground fault current is sent to a π transmitter A disposed near the right-phase current transformer. In device A, this current is connected to the device power supply 6 so that a special external power supply is not required.
used to operate each part.

Roughly speaking, a part of the earth fault current '1Affi is reduced to, for example, 1mA by the auxiliary current transformer 2, and then changed to a constant value by the voltage frequency converter 3.
It is converted into a pulse frequency signal of l+, for example, 20K H
It is assumed to be a Z pulse frequency signal. The number of pulses increases if the ground fault current is large, and decreases if the ground fault current is small, so the operating ground fault current range is wide and an external power source is not required.

Next, the pulse signal converted by the voltage frequency converter 3 described above is applied to an electro-optical converter 4 having a light emitting element such as a light emitting diode, and is converted into a pulsed optical signal.
Detector 1 at substation etc. via optical fiber via optical coupler 5
3. In addition, in order to check whether or not the optical fiber is disconnected, the optical signal generated by the light emitting element 7 of the detector L is transmitted through the optical fiber I\- on the normal side, and passed through the optical coupler 5 to detect the accident. The optical signal from the light emitting element is a pulsed signal given every 0.2 seconds, for example, but the optical signal from the electric-to-optical converter 4 is transmitted along with the electric current. Since there is a large difference in frequency between the frequency of the light and the light from the light emitting element 7, there is no 1.=ni gap 11' even when Φ is folded.

In this way, the optical signal from the optical coupler 5 is transmitted to the detector] 3, converted into a current by an optical-to-electrical converter 8 such as a photodiode, and appropriately amplified by an amplifier () to detect a ground fault. 18
- input to the central processing unit 10 as a fault detector; In the central processing unit 10, the optical signal from the light emitting element R-7 and the light from the electrical-to-optical converter 4 (no. , ■ If the occurrence of a ground fault current higher than the world current setting value (for example, 2A) is detected, a signal is output, the relay 11 is activated, and an alarm, etc. is activated. is a power source for operating each of the above-mentioned parts of the detector I3.

In addition, in FIG. 2, an auxiliary current transformer 2, a voltage frequency converter 3
, a waveform shaper 3a belonging to the voltage frequency converter 3, an electrical
A specific example of the main circuit connections of the ht transmitter [3 consisting of the optical conversion device 4] is shown.

〔Effect of the invention〕

As is clear from the explanation below, according to the present invention, the optical signal for detecting the IjJr line from the receiving end is converted into an optical signal proportional to the ground fault current t. Optical coupling with 11
) i etc., Q end (, etc.) is transmitted, so it is possible to always detect whether the optical fiber is cut or not.
At the time of 'I'1', an optical signal is sent from the receiving station such as 'aj'+'i', so the transmitter 111- does not require a power supply, and the installation location is limited. It is possible to achieve excellent effects in practical use, such as not being affected by damage.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of an embodiment of the underground power transmission line ground fault detection device according to the present invention, and FIG. 2 is a circuit connection diagram of the embodiment of the feeder of FIG. Δ: Transducer B: Detector 1: Zero-phase current transformer 2: Auxiliary current transformer (3: Voltage frequency converter 4: Electrical-optical converter 5/optical coupler 6: Power source 7: Light emitting element 8: Optical-electrical converter: Amplifier IO = Central processing unit: Relay

Claims (1)

[Claims] An optical signal proportional to the ground fault current from a zero-phase current transformer that occurs due to a ground fault in an underground power transmission line and an optical signal for disconnection detection from the receiving end are optically coupled and sent to the receiving end via optical fiber. A disconnection of an optical fiber for transmitting a signal for detecting a ground fault accident in an underground power transmission line, which is characterized by detecting a ground fault current by transmitting the light and converting the transmitted light into an electrical signal, and detecting the presence or absence of a break in the optical fiber. Detection method.