JPH01277773A - 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 and an output of the partial discharge sound detecting sensor is delayed. 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 is inputted to a detection signal checking circuit 12, a trigger pulse generating circuit 26 outputs a control signal to make a switch circuit 23 operate. The circuit 23 turns a switch OFF to break a circuit which transmits an output of the sensor 10 to a signal processing circuit 11. A delay circuit 22 is inserted before the circuit 23, a detection signal of the sensor 10 is thereby delayed for a prescribed time and the input of the external noise to the circuit 11 is checked. By this constitution, 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. 4, 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 groove body in FIG. 4 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 at an appropriate timing.

(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, the partial discharge sound detection sensor and the signal processing circuit. a detection signal blocking circuit including a delay circuit inserted between the circuit and an external noise sensor for detecting sudden external noise; When this occurs, the apparatus is characterized in that it operates to block input of the detection signal from the partial discharge sound detection sensor delayed by the delay circuit for a predetermined period of time 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, a transducer 10b that converts the acoustic vibrations into electrical signals, 13b. For the transducers 10b and 13b, for example, PZT, which is a known piezoelectric ultrasonic vibrator, is used. Both sensors 10 and 13 are integrated into the sensor case 1.
4 and is fixed. In this sensor case 14, the partial discharge sound output sensor 10 is supported and fixed to the outer surface of the object to be inspected, for example, the cable connection portion 1, so that its horn 10a can be brought into close contact. 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.

The output of the partial discharge sound detection sensor 10 is amplified by a preamplifier 16, and connected to be input to the signal processing circuit 11 via a filter 17 and a detection signal blocking circuit 12. On the other hand, the output of the external noise sensor 13 is amplified by a preamplifier 18 and connected to be input to the detection signal blocking circuit 12 via a filter 19 .

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

Now, the detection signal blocking circuit 12 includes an amplifier 21 and a delay circuit 22 inserted in series in a circuit that receives the detection signal of the partial discharge sound detection sensor 10 and transmits it to the signal processing circuit 11. It has a switch circuit 23. The delay circuit 22 is a circuit that can delay an input signal for a predetermined period of time. For example, in this embodiment, the delay circuit 22 is a circuit that operates to delay a detection signal input from the partial discharge sound detection sensor 10 by several milliseconds. . This delay time differs depending on various external conditions such as circuit configuration and measurement conditions, so it is recommended to set it to an appropriate value when designing the partial discharge detection device, or use a variable delay circuit and select an appropriate value each time. You may also do so.

Further, the switch circuit 23 is, for example, a switch that is inserted in series in a transmission path of a detection signal from the partial discharge sound detection sensor 10 to the signal processing circuit 11 and turns 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. Furthermore, this switch circuit 23
is a circuit that processes the output of the partial discharge sound detection sensor 10 substantially so that it does not reach the signal processing circuit 11 by short-circuiting its input terminal or short-circuiting its output terminal according to a control signal. Bye.

In addition, the detection signal blocking circuit 12 is provided with an amplifier 25 that receives and receives the detection signal from the external noise sensor 13, and a trigger pulse generation circuit 26. This amplifier 25
The amplification degree of is adjusted by the amplification degree adjustment circuit 27.

The trigger pulse generation circuit 26 is a circuit that outputs a control signal for operating the switch circuit 23 when the external noise sensor 13 detects sudden external noise. That is,
A switch-off operation is performed to prevent transmission of this detection signal.

The operation of the amplification adjustment circuit 27 of the detection signal blocking circuit 12 is controlled by a microprocessor 28 provided externally. This microprocessor 28 is also used, for example, to analyze a partial discharge sound detection signal input to the signal processing circuit 11.

First, the basic operating principle of the partial discharge detection device having the above configuration will be explained.

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.

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 formed on the outer surface of the cable connection part 1, it does not detect partial discharge sound.
Figure 2(b)]. In this case, partial discharge sound detection sensor 1
The detection signal outputted by 0 is input to the signal processing circuit 11 via the detection signal blocking circuit 12 [FIG. 2(C)], and analysis of the partial discharge sound is proceeded.

Next, when an external noise as explained in FIG. 4 suddenly occurs, the partial discharge sound detection sensor 1O 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 trigger pulse generation circuit 26 outputs a control signal to operate the switch circuit 23. That is, the switch circuit 23 uses the control signal to
The switch is turned off to cut off the circuit that has been transmitting the output of the partial discharge sound detection sensor 10 to the signal processing circuit 11. As a result, the input signal of the signal processing circuit 11 becomes 0FF (zero) for that time [FIG. 2(C)].

Thereafter, when the switch of the switch circuit 23 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 is input, and the detection and analysis of the partial discharge sound can be continued.

By the way, when this partial discharge detection device is actually used to detect partial discharge sounds, a predetermined time lag as shown in Figure 3 occurs between the detection signals of each part shown in Figure 2. .

That is, the detection signal of the external noise sensor 13 may be inputted with a delay of a predetermined time t with respect to the detection signal of the partial discharge sound detection sensor 10 [FIGS. 3(a) and 3(b)]. According to experiments, this time was less than 1 millisecond, but as a result, the start of the switch-off operation of the switch circuit 23 was delayed [Fig. 3 (d)], and the signal processing circuit 11 was affected by external noise. Part of the information is input [Figure 3 (C)]. On the contrary, there are cases where the switch-off operation is earlier than the input of the control signal to the partial discharge sound detection sensor 1o. However, in that case, if the total switch-off time is sufficiently long compared to the external noise generation time, no external noise will be input to the signal processing circuit 11.

The reason why there is a difference in the input timing of the detection signal of the partial discharge sound detection sensor IO and the detection signal of the external noise sensor 13 is considered to be due to the difference in distance between the sound source and each sensor.

Therefore, in the partial discharge detection device of the present invention, a delay circuit 22 is inserted in front of the switch circuit 23 to delay the detection signal of the partial discharge sound detection sensor 10 for a predetermined period of time or more, so that external noise can be prevented from processing the signal. The input to circuit 11 is effectively blocked. Note that when the external noise sensor 13 detects external noise, the switch circuit 23 turns off the switch while the external noise is at a predetermined level or higher. However, in order to ensure the switch operation and stabilize the signal blocking operation, it is preferable to continue the switch-off operation for a certain period of time when external noise is input, even if the external noise disappears instantaneously. In this case, since the switch-off time is sufficiently long compared to the external noise generation time, there is no problem with the blocking operation, as explained above. Therefore, the delay time of the delay circuit 22 may be selected to a value that is longer than the actual time difference between the detection signals of both sensors and that takes into account the switch-off time of the switch circuit.

(Effects of the Invention) The partial discharge detection device of the present invention described above includes an external noise sensor in addition to the partial discharge sound detection sensor, and the detection signal of the external noise sensor causes the partial discharge sound detection sensor to generate a signal. Since the input of the detection signal to the processing circuit is blocked, 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.

Further, since a delay circuit is provided to delay the output of the partial discharge sound detection sensor, there is no possibility that external noise may be input due to a delay in switch operation and cause a misdiagnosis.

[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 operating principle, and FIG. 3 is a diagram explaining its specific operation. FIG. 4 is an explanatory diagram illustrating the problems of the conventional partial discharge detection device. 10------ Partial discharge sound detection sensor, 11-
------m-signal processing circuit, 12-------m-detection signal blocking circuit, 13----
--m-External noise sensor, 22--One delay circuit. Figure 2 Figure 3

Claims (1)

[Claims] A detection signal blocking device including a partial discharge sound detection sensor, a signal processing circuit for processing a detection signal of the partial discharge sound detection sensor, and a delay circuit inserted between the partial discharge sound detection sensor and the signal processing circuit. circuit, and an external noise sensor that detects sudden external noise, and the detection signal blocking circuit detects the partial discharge delayed by the delay circuit for a predetermined time when the external noise sensor detects the sudden external noise. A partial discharge detection device, characterized in that it operates to block input of the detection signal from the sound detection sensor to the signal processing circuit.