JP2005283523A - Device for detecting occurrence of partial discharge - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an inexpensive device of simple constitution capable of determining accurately occurrence of partial discharge in a cable way, without generating erroneous detection, and capable of breaking the cable way or issuing an alarm. <P>SOLUTION: This device for detecting the occurrence of the partial discharge includes a means for detecting about 450kHz-2MHz of high-frequency current generated in the cable way by a current detecting part, and for generating a detection signal when the high-frequency current detected by the current detecting part is a prescribed threshold value or more. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

The present invention relates to a technique for detecting partial discharge such as tracking of a plug / outlet or the like, intermittent short-circuit of an interphase electric wire, or spark discharge due to intermittent energization of a poorly connected portion.

Conventionally, as a device for detecting the occurrence of such partial discharge, both frequency components are detected by detecting both the commercial frequency component and the high-frequency component of the short-circuit current generated by the short circuit as disclosed in Patent Document 1. Some switches cut off the electrical circuit.

JP-A-14094

However, in the conventional method, the kHz order is detected as the high-frequency current component. For example, a power line carrier signal using a frequency of 450 kHz or less and noise such as an inverter / microwave oven are superimposed on the electric circuit. There was a high possibility of false detection when an inrush current at the start of an incandescent lamp or motor flowed there.

Therefore, the object of the present invention is to reduce the cost of a device that detects the occurrence of partial discharge in the electric circuit and generates a cutoff or alarm without making a false detection more accurately. Is to provide.

In order to achieve the above object, in claim 1 of the present invention, a high frequency current of approximately 450 kHz to 2 MHz generated in the electric circuit is detected by a current detection unit, and the high frequency current detected by the current detection unit exceeds a predetermined threshold value. Therefore, the present invention provides a device for detecting the occurrence of partial discharge including means for generating a detection signal.

Further, in claim 2, a plurality of high-frequency currents having different frequencies among high-frequency currents of approximately 450 kHz to 2 MHz generated in the electric circuit are detected by the current detection unit, and the detected plurality of high-frequency currents are all equal to or greater than a predetermined threshold value. An apparatus for detecting the occurrence of partial discharge including means for generating a detection signal is provided.

Furthermore, in claim 3, a high-frequency current of approximately 450 kHz to 2 MHz generated in the electric circuit is detected by the current detection unit, and it is determined whether the high-frequency current is equal to or greater than a predetermined threshold at every frequency interval. The present invention provides an apparatus for detecting the occurrence of partial discharge including means for generating a detection signal when the number of intervals of the given frequency reaches a predetermined number.

According to experiments by the inventors of the present invention, it has been newly found that when a tracking phenomenon occurs in an electric circuit, a current containing a high-frequency component of 2 MHz or less flows through the electric circuit almost uniformly.

The inventor observed the current waveform before and after the occurrence of the tracking phenomenon occurring in the insulator between the plug blades, using the circuit device shown in FIG. The tracking phenomenon was caused by repeatedly dropping ammonium chloride solution between plug blades with a dropping device. In addition, as a result of observing the current waveform flowing in the electric circuit when using home appliances with the circuit of FIG. 6 and comparing the relationship between the frequency and current magnitude in graphs, I found that there was a difference.

FIG. 7 shows a comparison of frequency-current characteristics before tracking (Normal in the figure) and after tracking (Tracking in the figure) in one graph, FIG. 8 shows home appliance A (refrigerator), and FIG. , Home appliance B (electric pot), FIG. 10 shows home appliance C (laser printer), FIG. 11 shows home appliance D (CRT), and FIG. 12 shows frequency-current characteristics of home appliance E (fluorescent lamp). .

FIG. 7 shows that after tracking occurs, the current of about 2 MHz or less is about 10 dB larger than before the occurrence. It was found that the current due to the use of the home appliances of FIGS. 8 to 12 is almost the same as that before the tracking of FIG. Therefore, if the difference in the magnitude of the high-frequency current in the band of 2 MHz or less can be detected, the occurrence of tracking may be detected. In addition to tracking, there is a possibility that partial discharge can be detected in the same manner, for example, when an electrical short-circuit between the cores of the electric wires, or when a contact is interrupted due to a partial disconnection or poor connection, causing sparks.

In general, it is said that most of current noise due to use of home appliances, inverter devices, microwave ovens, etc. is a component of 200 kHz or less. Further, communication by power line carrier is regulated to 450 kHz or less under the current law, and there is only a possibility that the frequency band of 2 MHz to 30 MHz will be relaxed in the future.

In the frequency band of 450 kHz to 2 MHz, the presence of radio signals such as AM radio and amateur radio can be considered, but the influence does not appear from the measurement results of FIGS. 8 to 12 by the circuit device of FIG.

Therefore, according to the first aspect of the present invention, when a high frequency current of approximately 450 kHz to 2 MHz generated in the electric circuit is detected by the current detection unit and the high frequency current detected by the current detection unit is equal to or greater than a predetermined threshold, Since a device that detects the occurrence of partial discharge, including means for generating a signal, has been provided, it is possible to accurately determine that tracking has occurred in the electric circuit without being affected by high-frequency noise that flows due to the use of inverter equipment, power line carrier, etc. This has the effect of providing an alarm or a device that interrupts the electric circuit.

According to the invention of claim 2, a plurality of high-frequency currents having different frequencies among the high-frequency currents of approximately 450 kHz to 2 MHz generated in the electric circuit are detected by the current detector, and the detected plurality of high-frequency currents are all predetermined. Since a device for detecting the occurrence of partial discharge including means for generating a detection signal when the threshold value is exceeded is provided, it can be detected in a pseudo manner that a high-frequency current component of 2 MHz or less is uniformly included. In addition to the effect of claim 1, there is an effect that it can be detected more accurately.

Furthermore, according to the invention of claim 3, a high-frequency current of approximately 450 kHz to 2 MHz generated in the electric circuit is detected by the current detection unit, and it is determined whether the high-frequency current is equal to or greater than a predetermined threshold at every arbitrary frequency interval. Since a device for detecting the occurrence of partial discharge including means for generating a detection signal when the number of frequency intervals that were equal to or greater than the threshold value has reached a predetermined number, a high-frequency current component of 2 MHz or less is It is possible to more accurately detect that it is included, and it is possible to detect more accurately than in claim 2.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 shows that a high-frequency current of approximately 450 kHz to 2 MHz generated in the electric circuit shown in the first embodiment of the present invention is detected by a current detection unit, and the high-frequency current detected by the current detection unit is equal to or greater than a predetermined threshold value. FIG. 4 is a block diagram showing an apparatus for detecting the occurrence of partial discharge including means for generating a detection signal. The block diagram includes an electric circuit 1, a current detection unit 2, a current-voltage conversion unit 3, a filter unit 4, a partial discharge determination unit 5, and a treatment unit 20.

The current detector 2 detects the current flowing through the electric circuit 1 and outputs an alternating current.

The current-voltage conversion unit 3 converts the alternating current output from the current detection unit 2 into an alternating voltage, and specifically converts the alternating current into an alternating voltage through a resistor.

The filter unit 4 passes an AC voltage of approximately 450 kHz to 2 MHz by processing the AC voltage output from the current-voltage conversion unit 3 with a bandpass filter.

The partial discharge determination unit 5 measures the AC voltage output from the filter unit 4, and determines that partial discharge has occurred in the electric circuit when it is equal to or greater than a predetermined threshold value, and outputs a detection signal.

According to the detection signal output from the partial discharge determination unit 5, the device cuts off the electric circuit at 20 treatment units or issues an alarm with a lamp.

FIG. 2 shows a second embodiment of the present invention, in which a high frequency current of approximately 450 kHz to 2 MHz generated in an electric circuit is detected by a plurality of current detection units having different detection frequencies, and all the high frequency currents detected by each current detection unit are predetermined. It is a block diagram which shows the apparatus which detects generation | occurrence | production of the partial discharge including the means to generate | occur | produce a detection signal when it is more than this threshold value. The block diagram includes an electric circuit 1, a current detection unit 2, a current-voltage conversion unit 3, a filter unit 6, a filter unit 7, a partial discharge determination unit 8, and a treatment unit 20.

The current detector 2 detects the current flowing through the electric circuit 1 and outputs an alternating current.

The current-voltage conversion unit 3 converts the alternating current output from the current detection unit 2 into an alternating voltage, and specifically converts it into an alternating voltage through a resistor.

The filter unit 6 allows the AC voltage from about 450 kHz to 1 MHz to pass through band-pass filter processing of the AC voltage output from the current-voltage conversion unit 3.

The filter unit 7 passes an AC voltage of approximately 1 MHz to 2 MHz by band-pass filtering the AC voltage output from the current-voltage converter 3.

The partial discharge determination unit 8 measures the AC voltage output from the filter unit 6 and the filter unit 7, and determines that partial discharge has occurred in the electric circuit when both voltage values are equal to or greater than a predetermined threshold value. Output a signal.

According to the detection signal output from the partial discharge determination unit 8, the device cuts off the electric circuit at 20 treatment units or issues an alarm with a sound or an alarm lamp.

In the second embodiment, the current in the frequency range of approximately 450 kHz to 2 MHz is detected by dividing it into two frequency ranges, and it is determined that a partial discharge has occurred in the electric circuit. However, it is divided into two or more frequency ranges. It may be detected and determined. Further, although FIG. 2 has been described with one current detection unit, a current detection unit may be provided for each frequency to be detected.

FIG. 3 shows a third embodiment of the present invention, in which a high-frequency current of approximately 450 kHz to 2 MHz generated in the electric circuit is detected by a current detection unit, and whether or not the high-frequency current is greater than or equal to a predetermined threshold at every arbitrary frequency interval. FIG. 6 is a block diagram showing an apparatus for detecting the occurrence of partial discharge including means for generating a detection signal when the number of frequency intervals that are equal to or greater than a threshold value reaches a predetermined number. The block diagram includes an electric circuit 1, a current detection unit 2, a current-voltage conversion unit 3, a filter group unit 9, a partial discharge determination unit 10, and a treatment unit 20. The filter group 9 is composed of a number of filters 901, 902, 903.

The current detector 2 detects the current flowing through the electric circuit 1 and outputs an alternating current.

The current-voltage conversion unit 3 converts the alternating current output from the current detection unit 2 into an alternating voltage, and specifically converts it into an alternating voltage through a resistor.

The filter group unit 9 divides the AC voltage output from the current-voltage conversion unit 3 into a number of filters at an arbitrary frequency interval in a range of approximately 450 kHz to 2 MHz, and a signal that has passed through the filter is a partial discharge determination unit 10. Is output.

The partial discharge determination unit 10 counts the number of filters whose output signals are equal to or greater than the threshold value in the individual filters 901, 902, 903,... Of the filter group unit 9, and when the number reaches a predetermined number, It is determined that a discharge has occurred, and a detection signal is output.

Based on the detection signal output from the partial discharge determination unit 10, the treatment unit 20 blocks the electric circuit or issues an alarm with a sound or a lamp.

FIG. 4 shows a fourth embodiment of the present invention, in which a high-frequency current of approximately 450 kHz to 2 MHz generated in the electric circuit is detected by a current detection unit, and whether the high-frequency current is equal to or greater than a predetermined threshold at every arbitrary frequency interval. FIG. 6 is a block diagram showing an apparatus for detecting the occurrence of partial discharge including means for generating a detection signal when the number of frequency intervals that are equal to or greater than a threshold value reaches a predetermined number. The block diagram includes an electric circuit 1, a current detection unit 2, a current-voltage conversion unit 3, a frequency spectrum conversion unit 11, a partial discharge determination unit 12, and a treatment unit 20.

The current detector 2 detects the current flowing through the electric circuit 1 and outputs an alternating current.

The current-voltage conversion unit 3 converts the alternating current output from the current detection unit 2 into an alternating voltage, and specifically converts it into an alternating voltage through a resistor.

The frequency spectrum conversion unit 11 converts the time spectrum of the AC voltage output from the current-voltage conversion unit 3 into a frequency spectrum and outputs the frequency spectrum to the partial discharge determination unit. That is, in the waveform change over time, the included frequency component and the signal magnitude are output to the partial discharge determination unit 12 as data.

The partial discharge determination unit 12 determines whether or not the frequency spectrum output from the frequency spectrum conversion unit 11 is equal to or greater than a predetermined threshold value for each arbitrary frequency interval in a band of approximately 450 kHz to 2 MHz. When the number of frequency intervals reaches a predetermined number, it is determined that partial discharge has occurred in the electric circuit, and a detection signal is output.

Based on the detection signal output from the partial discharge determination unit 12, the treatment unit 20 cuts off the electric circuit with a contact switching device or issues an alarm with a sound or a lamp.

According to the first embodiment described above, the partial discharge determination unit outputs a detection signal if a signal of one specific frequency is approximately equal to or greater than a predetermined threshold within a frequency band of approximately 450 kHz to 2 MHz. .

Further, according to the second embodiment, there are both a signal having a specific frequency within a frequency band of approximately 450 kHz to 1 MHz and a signal having a specific frequency within a frequency band of approximately 1 MHz to 2 MHz. For example, the partial determination unit outputs a detection signal.

Further, according to the third and fourth embodiments, it is determined whether or not the frequency is greater than or equal to a predetermined threshold at every arbitrary frequency interval in a band of about 450 kHz to 2 MHz, and the number of frequency intervals that are equal to or higher than the threshold is predetermined. Therefore, the detection signal is generated when the number reaches the number of the first and second embodiments, so that the entire frequency band of about 450 kHz to 2 MHz is increased from the first embodiment to the second embodiment, and further to the third and fourth embodiments. It is easy to detect the characteristic that the signal level is high.

It can be applied to a device that prevents a fire due to the tracking phenomenon by detecting that a partial discharge has occurred in the electric circuit due to the tracking phenomenon and outputting an alarm, or interrupting the electric circuit with a contact switching device.

In addition, it can detect the occurrence of partial discharge in the electric circuit due to intermittent short circuit between the core wires, half-disconnection or intermittent contact due to poor connection, and sparks, etc. It can also be applied to a device that prevents a fire by interrupting the electric circuit with a contact switching device.

1 is a circuit configuration diagram showing an embodiment of the present invention and claim 1; FIG. It is a circuit block diagram which shows this invention and the Example of Claim 2. It is a circuit configuration diagram showing an embodiment of the present invention and claim 3. It is a circuit block diagram which shows another Example of this invention and Claim 3. Measurement circuit for current flowing in the circuit during tracking and normal operation Measurement circuit for current flowing through the electrical circuit when using home appliances Frequency characteristics of current during normal operation and tracking Frequency characteristics of current when using home appliance A (refrigerator) Frequency characteristics of current when using home appliance B (electric pot) Frequency characteristics of current when using home appliance C (laser printer) Frequency characteristics of current when using home appliance D (CRT) Frequency characteristics of current when using home appliance E (fluorescent lamp)

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Electric circuit 2 Current detection part 3 Current-voltage conversion part 4 Filter part 5 Partial discharge determination part 6 Filter part 7 Filter part 8 Partial discharge determination part 9 Filter group part 901,902,903 .. Filter 10 Partial discharge determination part 11 Frequency Spectrum converter 12 Partial discharge determination unit 20 Treatment unit

Claims (3)

And a means for detecting a high frequency current of approximately 450 kHz to 2 MHz generated in the electric circuit by a current detection unit, and generating a detection signal when the high frequency current detected by the current detection unit is equal to or greater than a predetermined threshold value. A device that detects the occurrence of partial discharge. Among the high-frequency currents of approximately 450kHz to 2MHz generated in the electric circuit, a plurality of high-frequency currents having different frequencies are detected by the current detection unit, and a detection signal is generated when the detected plurality of high-frequency currents are all equal to or greater than a predetermined threshold value. An apparatus for detecting the occurrence of partial discharge, characterized by comprising means for A high-frequency current of approximately 450 kHz to 2 MHz generated in the electric circuit is detected by the current detection unit, and it is determined whether the high-frequency current is greater than or equal to a predetermined threshold at every frequency interval. An apparatus for detecting the occurrence of partial discharge, comprising means for generating a detection signal when the number reaches a predetermined number.