JPH01277776A - Detecting device of partial discharge - Google Patents

Abstract

PURPOSE:To facilitate the detection and analysis of a partial discharge sound, by a method wherein the input of a detection signal from a partial discharge sound detecting sensor to a signal processing circuit is checked by a detection signal of an external noise sensor. CONSTITUTION:When external noise occurs suddenly, both a partial discharge sound detecting sensor 10 and an external noise sensor 13 detect the noise simultaneously. When a detection signal of the sensor 13 inputs to a detection signal checking circuit 12, the signal is rectified by a rectifier circuit 18 and inputted to a peak value holding circuit 19. The circuit 19 raises the level of a control signal for a switch circuit 20 to a prescribed value or above. The circuit 20 is turned off to break a circuit which transmits an output of the sensor 10 to a signal processing circuit 11. According to this constitution, a useless signal due to the external noise is not inputted to the circuit 11, and thus the detection and analysis of a partial discharge sound are facilitated.

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical Field of the Invention) The present invention relates to a partial discharge detection device for detecting partial discharge generated inside an insulator or the like of an electric cable.

(Technical background of the invention and its problems) When a high voltage is applied to a dielectric (insulator), if there is an electrical defect such as a void inside the insulator, the electric field will concentrate in that part and cause electrical discharge.

For example, if such a partial discharge occurs in the insulator of a high-voltage cable for power transmission, the insulator will deteriorate from that part, and in the worst case, dielectric breakdown will occur. In order to prevent this, a method is known in which partial discharge occurring in the cable insulator is acoustically detected in advance. This belongs to a type of non-destructive testing method called the acoustic emission method.

Generally, when a partial discharge occurs, a discharge sound is generated from the discharge location. This discharge sound propagates in the cable insulation as a sound wave. Therefore, by bringing an acoustic detection element such as an ultrasonic sensor into contact with the outer periphery of the cable insulator, the location and degree of partial discharge can be detected.

However, when performing such acoustic detection, countermeasures against external noise become a particularly important issue.

That is, as shown in FIG. 3, when the partial discharge sound detection sensor 2 is brought into contact with the outside of the cable connection part 1, the partial discharge sound 5 generated by the defect 4 inside the insulator 3 is detected. ,
The sensor 2 simultaneously detects the noise 6 generated in the surrounding area, the sound 7 of falling objects, the noise 8 generated when the partial discharge sound detection sensor 2 is moved, and the like. This external noise not only interferes with partial discharge detection work, but also causes a false diagnosis that there is a defect in a normal insulator. In addition, illustration of the cable conductor in FIG. 3 is omitted.

Now, of the detection outputs of this partial discharge sound detection sensor 2, it is necessary to obtain only the detection output due to the discharge sound 5 actually generated by the defect 4 inside the insulator 3. To do this, noise other than discharge sound must be effectively removed from the detection output.

(Object of the Invention) The present invention has been made with attention to the above points, and includes a sensor that exclusively detects external noise in addition to a sensor for detecting partial discharge sound to detect partial discharge sound. It is an object of the present invention to provide a partial discharge detection device that removes external noise from a detection signal of a sensor for detecting a partial discharge.

(Summary of the Invention) A partial discharge detection device of the present invention includes: a partial discharge sound detection sensor; a signal processing circuit that processes a detection signal of the partial discharge sound detection sensor; It has a detection signal blocking circuit inserted between the processing circuit and an external noise sensor that detects sudden external noise, and when the external noise sensor detects sudden external noise, the detection signal blocking circuit detects sudden external noise. The present invention is characterized in that it operates to block input of the detection signal from the partial discharge sound detection sensor to the signal processing circuit.

(Embodiments of the Invention) Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a schematic configuration diagram showing an embodiment of a partial discharge detection device of the present invention.

This device includes a partial discharge sound detection sensor 10, a signal processing circuit 11, a detection signal blocking circuit 12, and an external noise sensor 13.

As shown in this figure, the partial discharge sound detection sensor 10 and the external noise sensor 13 both include horns 10a and 13a that receive acoustic vibrations, and a transducer 10b that converts the acoustic vibrations into electrical signals. , -13b. For the transducer fob 13b, for example, PZT, which is a known piezoelectric ultrasonic vibrator, is used. Both sensors 1O213 are housed and fixed together in the sensor case 14. In this sensor case 14, the partial discharge sound detection sensor 1o is
The horn 10a is supported and fixed to the outer surface of the object to be inspected, for example, the cable connection portion 1, so that the horn 10a can be brought into close contact with the outer surface. On the other hand, the external noise sensor 13 is supported and fixed such that its horn 13a is held in a non-contact state with a space 15 between it and the object to be inspected. Therefore, the horn 13a of the external noise sensor 13 is set so that the acoustic impedance of the portion facing the object to be inspected is significantly different from that of the horn 10a of the partial discharge sound detection sensor 10.

In addition, the output of the partial discharge sound detection sensor l○ is the amplifier 1
6, and is connected to be input to the signal processing circuit 11 via the detection signal blocking circuit 12. On the other hand, the output of the external noise sensor 13 is amplified by an amplifier 17 and connected to be input to the detection signal blocking circuit 12 .

Next, the signal processing circuit 11 includes, for example, an oscilloscope, a pen recorder, a measuring instrument, and various other circuits used to analyze input signal waveforms.

Further, the detection signal blocking circuit 12 includes a rectifier circuit 18, a peak hold circuit 19, and a switch circuit 20. The rectifier circuit 18 receives the output of the external noise sensor 13 via the amplifier 17, and includes a rectifier element for rectifying the output. The peak hold circuit 19 is a circuit that holds the peak value of the input signal at a level above a certain level for a predetermined period of time. This circuit consists of an integrating circuit, etc., and is often used in signal waveform measuring instruments, etc., and a more specific circuit explanation will be omitted. The switch circuit 20 is, for example, a signal processing circuit 11 for a detection signal of the partial discharge sound detection sensor 10.
It consists of a switch that is inserted in series in the transmission path to turn the circuit on and off. This may be, for example, an element called a reed relay, an amplifier circuit that can rapidly reduce the amplification degree of the input signal to zero by a control signal, or a switching element such as a transistor. Good too. In addition, the switch circuit 20 short-circuits its input terminal or short-circuits its output terminal in response to a control signal output from the peak hold circuit 19, so that the partial discharge sound detection sensor 10 is substantially
Any circuit that processes the output so that it does not reach the signal processing circuit 11 may be used. Of course, the rectifier circuit 18, peak hold circuit 19, etc. may be configured by digital circuits using a microprocessor.

The partial discharge detection device having the above configuration operates as follows.

FIG. 2 shows the waveforms of the detection signals detected by the partial discharge sound detection sensor 10 and the external noise sensor 13, and the input signal of the signal processing circuit 11. Using this figure and Figure 1 together,
The operation of the partial discharge detection device of the present invention will be explained.

First, when a partial discharge sound is emitted from the defect 4 in the insulator 3 of the cable connection part 1, the partial discharge sound detection sensor 10 detects this [FIG. 2(a)]. On the other hand, since the external noise sensor 13 is supported with a space 15 opened on the outer surface of the cable connection part l, it does not detect partial discharge sound.
(Fig. 2 (b)) In this case, the detection signal output from the partial discharge sound detection sensor 10 is manually input to the signal processing circuit 11 via the detection signal blocking circuit 12 [Fig. 2 (c) 1, Analysis of partial discharge sound is progressing.

Next, when an external noise as explained in FIG. 3 suddenly occurs, the partial discharge sound detection sensor 10 and the external noise sensor 13 simultaneously detect the noise [FIG. 2(a), (
b)]. Here, when the detection signal of the external noise sensor 13 is input to the detection signal blocking circuit 12, the signal is input to the rectifier circuit 1.
It is rectified by 8 and inputted to the peak hold circuit 19.

The peak hold circuit 19 thereby
The level of the control signal relative to 0 is raised to a predetermined value or higher. When the level of the control signal is raised, the switch circuit 20 turns off the switch and cuts off the circuit that has been transmitting the output of the partial discharge sound detection sensor 10 to the signal processing circuit 11. Since the peak hold circuit 19 holds this control signal above a predetermined value for a predetermined time determined from its circuit constants, the input signal of the signal processing circuit 11 becomes zero for that time [FIG. 2(C)].

Thereafter, when the switch of the switch circuit 20 is turned back on, the partial discharge sound detection sensor 1 is again connected to the signal processing circuit 11.
The detection signal output by 0 can be used manually to continue detecting and analyzing partial discharge sounds.

In reality, for example, when the detection signal output from the external noise sensor 13 is rectified by the rectifier circuit 18, it is approximately 2 V in the normal state.
When the output voltage of the rectifier circuit 18 exceeds 2V, the control signal level of the peak hold circuit 19 becomes 2V or more, and the switch of the switch circuit 20 is operated. An amplifier 17 is inserted to adjust the level of such a detection signal.

(Effects of the Invention) According to the present invention, the partial discharge detection device includes an external noise sensor in addition to the partial discharge sound detection sensor, and receives a signal from the partial discharge sound detection sensor based on the detection signal of the external noise sensor. Since the human input of the detection signal to the processing circuit is prevented, unnecessary signals due to external noise are not input to the signal processing circuit, which has the effect of facilitating the detection and analysis of partial discharge sound. Furthermore, it is possible to prevent erroneous diagnosis due to input of external noise into the detection signal.

[Brief explanation of the drawing]

Fig. 1 is a schematic configuration diagram showing an embodiment of the partial discharge detection device of the present invention, Fig. 2 is a waveform diagram of signals of each part to explain its operation, and Fig. 3 is a diagram of a conventional partial discharge detection device. It is an explanatory diagram explaining a problem. 10-1---Partial discharge sound detection sensor, 11-
----1--signal processing circuit, 12-------1 detection signal blocking circuit, 13--
-1--External noise sensor. 1 ° i (1 other person)

Claims (1)

[Claims] A partial discharge sound detection sensor, a signal processing circuit for processing a detection signal of the partial discharge sound detection sensor, a detection signal blocking circuit inserted between the partial discharge sound detection sensor and the signal processing circuit, an external noise sensor that detects sudden external noise, and the detection signal blocking circuit is configured to block the partial discharge sound from the partial discharge sound detection sensor to the signal processing circuit when the external noise sensor detects sudden external noise. A partial discharge detection device that operates to block input of a detection signal.