JP2650935B2 - Partial discharge location method - Google Patents

Description

The present invention relates to a method for locating a partial discharge.

(Prior Art) Conventionally, it has been widely performed to detect a partial discharge generated in a power cable, a power cable connection portion, or the like by an electric position locating method. In addition, an ultrasonic sensor detects mechanical vibration generated at the time of partial discharge, and localization of a position at which partial discharge occurs is also performed. Further, an electric position locating method and a position locating method using an ultrasonic sensor are used in combination.

(Problems to be Solved by the Invention) However, the conventional electrical position locating method requires preparation work such as stopping power transmission of a power cable system and connecting a high-voltage device such as a high-voltage capacitor. However, there is a problem that an expensive partial discharge measuring instrument or advanced measurement technology is required, and furthermore, measurement cannot be performed with sufficient sensitivity in a field environment with a lot of ambient noise, and the location accuracy is poor from the viewpoint of position location. On the other hand, a method for evaluating the position of the partial discharge by using an ultrasonic sensor has not yet been sufficiently established.

That is, in a power cable, a power cable connection portion, or the like, most of the medium through which ultrasonic waves generated by partial discharge pass is an insulator, and the speed of the ultrasonic waves passing through the insulator varies depending on the material of the insulator. I do. The speed of the ultrasonic wave also changes depending on the ambient temperature. Furthermore, the degree of change in ambient temperature (temperature characteristic) also differs depending on the material of the insulator.

For this reason, it is not easy to accurately determine the velocity of the ultrasonic wave transmitted through the insulator, which is necessary for locating the position where the partial discharge occurs.

Further, a method of calculating the velocity of the ultrasonic wave from the arrival time of the ultrasonic wave transmitted between two points separated by a predetermined distance in the insulator is also conceivable, but the measurement of the velocity is complicated, and the measured values of the distance and the time are different. Accurate speed measurement is not possible due to small errors.

For this reason, the speed of the ultrasonic wave transmitted through the insulator necessary for locating the position where the partial discharge has occurred differs depending on the material and the temperature of the insulator, and it is not easy to accurately and easily obtain the speed. There was a problem.

The present invention has been made in view of the above circumstances, and detects a signal waveform of an ultrasonic wave generated by partial discharge with at least five ultrasonic sensors to know the velocity of the ultrasonic wave transmitted through a medium. It is an object of the present invention to provide a partial discharge position locating method for locating a partial discharge without any partial discharge.

(Means for Solving the Problems) According to the present invention, in order to achieve the above object, ultrasonic waves generated by partial discharge are detected by at least five ultrasonic sensors, and the ultrasonic waves are detected by each ultrasonic sensor. The time is read, the shortest ultrasonic sensor is determined from the partial discharge occurrence position, each detection time difference of each ultrasonic sensor with respect to the shortest ultrasonic sensor is calculated, and the partial discharge occurrence position is calculated based on each calculated detection time difference. Is provided.

(Operation) At least five or more ultrasonic sensors are installed on the object for detecting the partial discharge, the ultrasonic waves generated at the time of the partial discharge are detected by each ultrasonic sensor, and this one ultrasonic sensor and another ultrasonic sensor are used. Each detection time difference of the ultrasonic signal waveform between the ultrasonic sensor and the ultrasonic sensor is obtained, and the partial discharge occurrence position is located from each detection time difference.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

FIG. 1 shows a position locating device for carrying out the present invention, in which five ultrasonic sensors 3a, 3b, 3c, 3d, 3e are mounted at a position where the ultrasonic wave at a connection 2 of a power cable 1 can be easily detected. The output of each ultrasonic wave is connected to the waveform storage device 5, and the waveform storage device 5 is connected to the arithmetic device 6. The waveform storage device 5 includes an AD converter and a digital memory. When a partial discharge is generated at the partial discharge occurrence position 4 of the connection portion 2, mechanical vibration is generated along with the partial discharge and becomes an ultrasonic wave, which propagates through the connection portion 2, and the ultrasonic sensors 3a, 3b, 3
After reaching c, 3d, 3e, it is converted into an electric signal. The analog electric signal is converted into digital waveform data by the A / D converter of the waveform storage device 5 and stored in the digital memory together with the arrival time at the waveform storage device 5. Arithmetic unit 6
Are the respective ultrasonic sensors 3a, 3b, 3c, 3 in the in-phase portion of the digital waveform described below from the above-described digital waveform and arrival time.
Calculate the arrival time difference between d and 3e. The coordinate axes X, Y, and Z are set as shown in FIG. 1, and the partial discharge occurrence position 4 is defined as (x, y,
z) Set the mounting positions of the five ultrasonic sensors to (x ₁ , y ₁ ,
z ₁ ), (x ₂ , y ₂ , z ₂ ), (x ₃ , y ₃ , z ₃ ), (x ₄ , y ₄ , z ₄ ),
And _{(x 5, y 5, z} 5).

Times at which the ultrasonic signal waveforms are detected by the five ultrasonic sensors are denoted by t ₁ ′, t ₂ ′, t ₃ ′, t ₄ ′, and t ₅ ′, respectively. Assuming that the velocity is v, the following five equations are obtained.

Here, s is the distance to the nearest ultrasonic sensor to the partial discharge generation position 4 (and if one th ultrasonic sensors 3a here), T ₂ ~T ₅ is other to the nearest ultrasonic sensor It is the detection time difference of the signal waveform of the ultrasonic sensor. Here, T ₂ = t ₂ ′ −t ₁ ′, T ₃ = t ₃ ′ −t ₁ ′, T ₄ = t ₄ ′ −
t ₁ ′, T ₅ = t ₅ ′ −t ₁ ′. Computing device is t ₁ '~t _5'
Determine the nearest ultrasonic sensor by selecting the smallest of the calculated time difference T ₂ through T _5. In the connection portion 2 of the power cable 1, most of the medium through which the ultrasonic waves generated by the partial discharge are transmitted is an insulator, and the speed of the ultrasonic waves transmitted through the insulator depends on the material, the ambient temperature, and the difference in the temperature characteristics depending on the material. Although different, the insulator through which most of the ultrasonic waves generated by the partial discharge passes has almost no difference in material and temperature depending on the location. Therefore, the speed of the ultrasonic waves is almost the same without any difference between the insulators. Since it can be considered that there is, the speed may be set as v.

Partial discharge generation position 4 of the coordinates in the case where the arithmetic unit 6 and the time difference between the ultrasonic signal waveform propagating the ultrasonic signal waveform propagating ultrasonic sensors 3a to the ultrasonic sensor 3b is T ₂ is calculated (x , y, z) are on the curved surface of the following equation (6).

That is, two ultrasonic sensors from the partial discharge occurrence position 4
The difference between the distances to 3a and 3b is given by T ₂ v. in this way,
The arithmetic unit 6 sequentially combines the equations (1) to (5),
For example, five unknown variables, that is, the coordinates (x, y, z) of the partial discharge occurrence position 4, the velocity v of the ultrasonic wave, and the distance s are obtained by solving by calculation using the known Newton-Raphson method.

Next, a specific example in which the position is actually located according to the present invention will be described. Five ultrasonic sensors a, b, c, d, and e were installed at the coordinate positions shown in Table 1 to actually generate partial discharge.

The time difference when the ultrasonic signal waveform generated by the partial discharge arrived at each ultrasonic sensor was obtained as shown in Table 2.
However, t ₁ ′ = 0.

From the above results, the coordinates of the partial discharge occurrence position were obtained by numerical calculation as x = 2.6 cm, y = 1.5 cm, and z = 15 cm. Here, the velocity v of the ultrasonic wave was 1880 m / sec, and the distance s was 15.6 cm. Later, the connecting portion 2 of the power cable 1 was disassembled and inspected, and it was confirmed that the above result was correct.

In addition, although the case where the connection part of the power cable causes dielectric breakdown due to partial discharge has been described as an example, the present invention can be applied to other objects that cause partial discharge.

(Effects of the Invention) As described above, according to the present invention, ultrasonic waves generated by partial discharge are detected by at least five ultrasonic sensors, and the detection time of each ultrasonic sensor is read for the ultrasonic waves, Determining the shortest ultrasonic sensor from the partial discharge occurrence position, calculating each detection time difference of each ultrasonic sensor with respect to the shortest ultrasonic sensor, and locating the partial discharge occurrence position based on each calculated detection time difference. Thus, the position of the partial discharge is easily and quickly located with high accuracy from the signals of the five ultrasonic sensors without having to know in advance the speed of the ultrasonic wave propagating in the medium in which the partial discharge position is to be located. At the same time, the velocity of the ultrasonic wave in the medium can be determined, and as a result, the effect of preventing the dielectric breakdown accident of the power cable, the connection portion of the power cable, etc. can be prevented. can get.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of a position locating device for implementing the present invention. 1 ... power cable, 2 ... connection part, 3a to 3e ... ultrasonic sensor, 4 ... partial discharge occurrence position, 5 ... waveform storage device, 6 ... arithmetic device.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Yoshio Maruyama 6 Yawata Kaigandori, Ichihara-shi, Chiba Furukawa Electric Co., Ltd. Inside Chiba Electric Wire Works (72) Inventor Yasuhiro Yamashita 6 Yawata-kaigandori, Ichihara-shi, Chiba Furukawa Electric (56) References JP-A-55-78249 (JP, A) JP 7-50144 (JP, B2)

Claims (1)

(57) [Claims] An ultrasonic wave generated by a partial discharge is detected by at least five ultrasonic sensors, a detection time of each ultrasonic sensor is read for the ultrasonic wave, and an ultrasonic wave arrived from a partial discharge generating position in a shortest time. Determining an ultrasonic sensor for detecting the difference, calculating each detection time difference of each ultrasonic sensor with respect to the shortest ultrasonic sensor, and locating a partial discharge occurrence position based on the calculated each detection time difference. Partial discharge location method.