JPH05188109A - Method for measuring partial discharge - Google Patents

Abstract

PURPOSE:To continuously monitor partial discharge of a cable or a high voltage machine without influence of ambient noise, etc., and also identify the location where the partial discharge occurs. CONSTITUTION:An optical fiber 5 is placed in the vicinity of insulators 1B, 2A of an object 1 to be measured to which high voltage is applied, and an end of the fiber 5 is connected to a light source 4 while the other end is connected to a partial discharge measuring device 7. If partial discharge occurs at a defective part of the insulators 1B, 2A of the object 1, ultrasonic waves are generated to cause a fluctuation of the plane of polarization of light propagated in the optical fiber 5. The partial discharge measuring device 7 detects the fluctuation of the plane of polarization to monitor and measure the partial discharge of the object 1. In addition, two optical fibers are placed in the vicinity of the insulator of the object to be measured, while one of the ends is connected to one end of the other fiber and folded at a loop part to detect time difference in fluctuations of the plane of polarization due to the partial discharge, whereby the location where the partial discharge occurs can be identified.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for measuring a partial discharge of a cable or a high voltage device, and more particularly to a method for measuring a partial discharge by utilizing a polarization plane variation of an optical fiber.

[0002]

2. Description of the Related Art As a method for measuring a partial discharge of a cable, a method shown in FIG. 5 has been known. In the figure, 101 is a cable which is a target of partial discharge measurement, 102 is a terminal end portion of the cable, 103 is a power supply terminal, 104 is a transformer, 105 is a measuring capacitor, 1
Reference numerals 06 and 107 are resistors for measurement, 108 and 109 are measuring instruments, and 110 is a ground capacitance of the cable 101.

The capacitance of the capacitor 105 in the figure is set to be approximately the same value as the ground capacitance 106 of the cable 101, and is connected to the terminal connection portion of the cable. Also,
The measuring resistor 107 is connected to the shield layer near the terminal connection of the cable 101. In the figure, when measuring the partial discharge of the cable 101, the power supply terminal 10
A commercial AC signal is added to 3 and, for example, 6 is added to the cable 101.
A high voltage of 0 kV is applied to the resistors 106 and 107.
The difference between the currents flowing through the measuring devices 108 and 109 is measured.

When a high voltage is applied to the cable 101, a corona discharge occurs and the air is discharged, but the noise generated by this discharge flows in both the resistors 106 and 107 and is canceled out, resulting in the measured values of the measuring instruments 108 and 109. There is no difference. When the cable 101 causes partial discharge, a difference occurs in the measurement values of the measuring devices 108 and 109 due to the pulse signal due to the partial discharge. By detecting this difference signal, the occurrence of partial discharge can be detected.

By the way, when a cable, etc. is actually used, if defects such as voids, protrusions, and foreign substances are present in the insulator, partial discharge occurs due to the application of electricity, and the electrical tree leads to dielectric breakdown. Therefore, it is very important for maintenance management to continuously monitor the insulation state when the cable or the like is actually used.

However, in the above-described conventional partial discharge measuring method, when measuring partial discharge, the charging of the cable of the object to be measured is stopped, the measuring capacitor 105 is attached, and the cable 101 is charged again. It is necessary to continuously monitor the partial discharge, and it is necessary to perform a dangerous work of installing a capacitor in a high voltage device.

Further, the partial discharge measurement according to the above method has a drawback in that it is easily affected by ambient noise and the reliable partial discharge measurement cannot be performed.

[0008]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned drawbacks of the prior art.
An object of the present invention is to provide a partial discharge measuring method capable of continuously monitoring a partial discharge of a cable or a high-voltage device without being affected by ambient noise and locating a place where the partial discharge occurs. And

[0009]

In order to solve the above-mentioned problems, the invention according to claim 1 of the present invention provides an optical fiber 5 in the vicinity of an insulator of an object to be measured 1 to which a high voltage is applied, An ultrasonic wave generated by a partial discharge generated in a defective portion of an insulator to be measured is configured to be detected by a polarization plane variation of light propagating in the optical fiber 5 to monitor and measure the partial discharge of the subject 1. Is.

According to a second aspect of the present invention, two optical fibers 5 are arranged in the vicinity of the insulator of the device under test 1 to which a high voltage is applied, and one end thereof is connected to form a loop. Part 5A
At the other end of the optical fiber 5,
The measuring means 7 for detecting the polarization plane fluctuation of the light propagating in the optical fiber 5 is provided, and the measuring means 7 detects the time difference of the polarization plane fluctuation due to the partial discharge generated in the defective portion of the insulator of the object to be measured 1. With this, it is configured to locate the location of the partial discharge.

[0011]

When a partial discharge occurs in the defective portion of the insulator of the object to be measured 1 to which a high voltage is applied, ultrasonic waves are generated. Due to this ultrasonic vibration, the optical fiber 5 arranged near the insulator vibrates and changes its main axis, causing polarization plane fluctuation in the light propagating through the optical fiber 5.

The invention according to claim 1 of the present invention detects the occurrence of partial discharge in the defective portion of the insulator of the object to be measured 1 by detecting the polarization plane variation. In addition, two optical fibers 5 are arranged in the vicinity of the insulator of the object to be measured 1, one end thereof is connected and folded back at the loop portion 5A, and the measuring means 7 is provided at the other end of the optical fiber 5. As a result, when partial discharge occurs in the defective portion of the insulator of the object to be measured 1, due to the transmission delay of the light propagating in the optical fiber 5, there are two polarization plane fluctuations having a time difference according to the place where the partial discharge occurs. To be detected.

According to the second aspect of the present invention, the location of the partial discharge is located by detecting the time difference between the two polarization plane fluctuations by the measuring means 7.

[0014]

FIG. 1 is a diagram showing a first embodiment of the present invention. In the figure, 1 is a cable, 1A is a cable conductor, 1B is a cable insulator, 1C is a cable shield, 2 is a connection portion, 2A is a connection portion insulator, 2B is a connection portion shield body, 3 is a cable conductor sleeve, Reference numeral 4 is a light source, 5 is an optical fiber, 6 is an optical fiber extra length storage box, and 7 is a partial discharge measuring instrument.

In FIG. 1, cables 1 are connected to each other via a connecting portion 2. A cable conductor 1A made of a stranded wire of the cable 1 is connected by a cable conductor sleeve 3, and a cable insulator 1B and a connection portion insulator 2A are provided around the cable conductor 1A and around the cable conductor sleeve 3 of the connecting portion 2. ing. Cable insulator 1
B and the periphery of the connection portion insulator 2A are covered with a cable shield body 1C and a connection portion shield body 2B, respectively.

Further, the optical fiber 5 is provided along the length direction on the peripheral surfaces of the cable insulator 1B and the connecting portion insulator 2A.
Is wound around, and the optical fiber 5 on each cable insulator 1B is connected with an extra length on the connector insulator 2A. The extra length of the optical fiber 5 is stored in the extra length storage box 6 on the connecting portion insulator 2A. Further, one end of the optical fiber 5 is connected to the light source 4, and the other end is connected to the partial discharge measuring instrument 7
It is connected to the.

FIG. 2 is a diagram showing the structure of a partial discharge measuring system according to the first embodiment of the present invention. In the figure, 1 is a cable, 2 is a connection part, 4 is a light source, 5 is an optical fiber, 8 is a polarizer, 9 is a photoelectric converter, 10 is a signal processing part, 11 is an alarm part, and 12 is a terminal connection. The same parts as those in FIG. 1 are designated by the same reference numerals. Also, FIG.
2 corresponds to the polarizer 8, the photoelectric converter 9, the signal processing unit 10, and the alarm unit 11 in FIG.

In FIG. 1, the area around the cable 1 is shown in FIG.
The optical fiber 5 is wound as shown in FIG. 3, and one end of the optical fiber 5 is connected to the light source 4 composed of, for example, a semiconductor laser.

The other end of the optical fiber 5 is input to a polarizer 8 for detecting polarization fluctuation of light, and the output of the polarizer 8 is converted into an electric signal by an opto-electric converter 9. The electric signal converted by the optical-electrical converter 9 is given to the signal processing unit 10,
Occurrence of partial discharge is detected based on the converted electric signal. The alarm unit 11 issues an alarm when the cable 1 is partially discharged.

The operation of the first embodiment of the present invention will be described below with reference to FIGS. The output light generated by the semiconductor laser of the light source 4 reaches the other end of the cable 1 through the optical fiber 5, enters the polarizer 8 of the partial discharge measuring instrument 7, and is converted into an electric signal by the opto-electric converter 9. It Cable 1
When no partial discharge occurs in the optical fiber 5, the polarization plane does not change in the optical fiber 5, the same light as that generated by the light source 4 enters the polarizer 8, and the opto-electric converter 9 Does not generate a partial discharge detection signal.

When a partial discharge is generated from the defective portion of the cable 1, the air in the void in the defective portion of the cable rapidly expands and an ultrasonic wave is generated. By this ultrasonic vibration,
The optical fiber 5 wound around the cable vibrates and changes its main axis, so that the light emitted from the light source 4 changes in the plane of polarization. This polarization fluctuation is caused by the partial discharge measuring instrument 7
Is detected by the polarizer 8 and converted into an electric signal by the opto-electric converter 9.

The output of the opto-electric converter 9 is the signal processing unit 10.
Is compared with a predetermined value, partial discharge occurs, and when the output of the photoelectric converter 9 exceeds the predetermined value, the signal processing unit 10 generates an output. The output of the signal processing unit 10 is given to the alarm unit 11 to notify that the partial discharge has occurred.

According to this embodiment, by disposing the optical fiber along the length direction on the cable insulator, it is possible to detect the partial discharge generated in any of the cables. It is possible to continuously measure partial discharge without stopping the power. Moreover, since the optical fiber is not affected by electrical external noise, the partial discharge can be reliably measured.

FIG. 3 is a diagram showing a second embodiment of the present invention. In the present embodiment, in a partial discharge measuring method using an optical fiber, a portion where a partial discharge has occurred can be located. It is a thing. In FIG. 3, the same components as those in FIG. 1 are designated by the same reference numerals. In this embodiment, two optical fibers are wound around the cable 1,
The light source 4 and the partial discharge measuring instrument 7 are provided at one end of the cable 1, and the loop portion 5A of the optical fiber 5 is provided at the other end of the cable 1.

FIG. 4 is a diagram for explaining the orientation principle of the partial discharge occurrence place in this embodiment, and FIG. 4A is a waveform observed by the partial discharge measuring instrument 7 when the partial discharge occurs in the cable 1. FIG. 3B is a diagram schematically showing FIG. Next, the operation of this embodiment will be described with reference to FIGS. In FIG. 3, one end A of the cable 1
The light generated by the light source 4 provided at the point reaches the other end B point of the cable 1 via the optical fiber 5. Then, it is folded back at the loop portion 5A provided at the other end B point of the cable 1, reaches the one end point A of the cable again through the optical fiber 5, and is input to the partial discharge measuring instrument 7.

Here, when partial discharge occurs at point F in FIG. 4b, polarization plane variation occurs in the light propagating in the optical fiber 5 at points C and D of the optical fiber 5. Due to this partial discharge, first, the polarization plane fluctuation of the optical signal detected at the point D of the optical fiber 5 is input to the partial discharge measuring instrument 7 via the optical fiber 5. Then, the fluctuation of the optical signal detected at the point C of the optical fiber 5 reaches the point B of the cable 1 from the partial discharge occurrence point F, is folded back at the loop portion 5A of the point B, and is partially discharged via the optical fiber 5. It is input to the measuring device 7.

Now, the time required for the optical signal to reach the point D from the point C to the point B in FIG.
(sec), the fluctuation of the optical signal observed by the partial discharge measuring device is 2 at an interval of time T (sec) as shown in FIG. 4a.
It is observed once. Then, if the velocity of light propagating through the optical fiber 5 is V (m / s) and the distance between the F point and the B point is L (m), the following formula is established.

T · V = 2L Therefore, the distance from the point B to the partial discharge generation point F can be obtained by L = T · V / 2. Therefore, when the partial discharge occurs, by obtaining the variation interval T of the optical signal detected by the partial discharge measuring instrument 7, the place where the partial discharge occurs can be located.

In the above embodiment, an example in which the optical fiber is wound around the cable to measure the partial discharge is shown, but the present invention is not limited to the above embodiment. For example, the optical fiber is connected to the cable. Arranged alongside,
If the optical fiber is arranged at a position where the ultrasonic vibration due to the partial discharge can be detected when the partial discharge occurs in the cable, the same effect as that shown in the above embodiment can be obtained.

The above-mentioned first and second embodiments show the case where the present invention is applied to the measurement of the partial discharge of the cable, but the present invention is limited to the above-mentioned embodiments. However, the present invention can also be applied to a partial discharge measurement method for high-voltage equipment such as transformers and generators. When the present invention is applied to the partial discharge measurement of a transformer, the partial discharge can be detected by disposing an optical fiber along the winding line of the transformer. Moreover, by using two optical fibers as shown in the second embodiment, it becomes possible to locate the location of the partial discharge in the transformer.

[0031]

As is clear from the above description,
In the present invention, since the ultrasonic vibration generated when the partial discharge occurs is detected by the polarization plane variation of the optical fiber, the partial discharge of the entire cable length under actual use is not affected by the external electrical noise. Can be continuously measured with high sensitivity.

Further, two optical fibers are arranged near the insulator to be measured to which a high voltage is applied, and
It is possible to locate the location of the partial discharge by connecting one end of the optical fiber and looping it back at the loop portion and detecting the time difference of the polarization plane fluctuation by the measuring means provided at the other end of the optical fiber.

[Brief description of drawings]

FIG. 1 is a diagram showing a first embodiment of the present invention.

FIG. 2 is a configuration diagram of a measurement system according to a first embodiment.

FIG. 3 is a diagram showing a second embodiment of the present invention.

FIG. 4 is a diagram illustrating the principle of the second embodiment.

FIG. 5 is a conventional example.

[Explanation of symbols]

 1 Cable 1A Cable Conductor 1B Cable Insulator 1C Cable Shield 2 Connector 2A Connector Insulator 2B Connector Shield 3 Cable Conductor Sleeve 4 Light Source 5 Optical Fiber 6 Optical Fiber Extra Length Storage Box 7 Partial Discharge Measuring Instrument 8 Polarizer 9 Optical-electrical converter 10 Signal processing section 11 Alarm section 12 Termination connection section

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Akira Fujisaki 2-6-1, Marunouchi, Chiyoda-ku, Tokyo Furukawa Electric Co., Ltd.

Claims (2)

[Claims] 1. A partial discharge generated at a defective portion of the insulator of the object to be measured (1) by disposing an optical fiber (5) near the insulator of the object to be measured (1) to which a high voltage is applied. The partial discharge measuring method characterized by detecting the ultrasonic wave by the polarization plane variation of the light propagating in the optical fiber (5) and monitoring and measuring the partial discharge of the object to be measured. 2. Two optical fibers (5) are arranged in the vicinity of the insulator of the device under test (1) to which a high voltage is applied, one end of which is connected and folded back at the loop part (5A). With
At the other end of the optical fiber (5), a measuring means (7) for detecting the polarization plane fluctuation of the light propagating in the optical fiber (5) is provided, and it is generated in the defective part of the insulator of the measured object (1). A partial discharge measuring method characterized by locating a place where a partial discharge occurs by detecting a time difference of polarization plane fluctuation due to the partial discharge by a measuring means (7).