JPH08129047A - Microwave sensor - Google Patents

Abstract

PURPOSE: To easily and accurately obtain a microwave sensor which resists against disturbance and detects discharge in real time by providing a BPF (Band-pass filter) for passing a specific frequency of a microwave signal received by an antenna. CONSTITUTION: A microwave signal f1 with a power of level P1 generated by the discharge inside an equipment is received by an antenna 3 and the signal is increased to a power of level P2 by the gain and is outputted. The signal f1 passes through a high-frequency band BPF 5a and the output is reduced to a level P3 due to the filter loss but is amplifier to a level P4 by a low-noise amplifier 6. Further, after passing only a signal component required by a BPF 5b, a microwave signal is directly converted to a video signal (level V1) by a detector 10. The video signal is amplified to the level V2 by an amplifier 11 and is outputted from an output terminal 13. The outputted signal is observed by an observation equipment such as an oscilloscope.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a device for detecting discharge caused by deterioration or abnormality of electric equipment.

[0002]

2. Description of the Related Art A dielectric breakdown accident, which is one of the serious accidents in electric power equipment, is often accompanied by the occurrence of partial discharge as a precursory phenomenon. Therefore, if the partial discharge is detected, it is possible to detect the insulation abnormality of the power device at an early stage in a minor state that does not result in a dielectric breakdown accident. Therefore, preventive maintenance technology for electric power equipment is emphasized, and it is required to install a sensor for failure diagnosis in the electric power equipment. In the case of partial discharge due to insulation deterioration, etc., when discharge occurs in electric power equipment, electromagnetic waves, electromagnetic field fluctuations, discharge pulse current, discharge noise, and scientific changes in the insulating medium occur. Various partial discharge detection methods utilizing the phenomenon have been proposed.

9 and 10 are edited by the Institute of Electrical Engineers of Japan: "Present state and trend of preventive maintenance technology for transformers", Technical Report of Institute of Electrical Engineers of Japan (Part II) No. 344, August 1990, (Transformer Preventive Maintenance Survey Special Committee), which is a configuration diagram showing a conventional discharge detection method by detecting a discharge current, in which 21 is a target device for which discharge is to be detected. , 22 is a high voltage capacitor, 23 is a pulse transformer, 24 is an amplifier, 25
Is an observation instrument such as an oscilloscope. Next, the operation will be described. A high voltage capacitor 22 is connected to the target device 21 and is grounded via a pulse transformer 23. The potential vibration due to the discharge inside the target device 21 causes the high voltage capacitor 22
Charging / discharging pulse current of the pulse transformer 23
Is converted into a voltage by, and further amplified by an amplifier 24 and observed by an oscilloscope 25 or the like.

FIG. 10 is a block diagram showing a discharge detecting method by detecting another discharge current. In the figure, 21 is a target device for which discharge is to be detected, 26 is a Rogowski coil, and 2 is a target device.
Reference numeral 4 is an amplifier, and 25 is an observation device such as an oscilloscope.

Next, the operation will be described. Target device 21
A pulse current such as a discharge is taken out by the Rogowski coil 26 or the like electromagnetically coupled to the grounding wire of No. 2, amplified by the amplifier 24, and observed by the oscilloscope 25 or the like.

In either method, the frequency is from several hundred KHz to 1
In a wide band of about MHz, a circuit connected to a device by a conductor catches the generated high frequency vibration over a wide range in a distributed constant network connected by space capacitance. Therefore, it is extremely difficult to discriminate the internal discharge and the external noise, which are originally desired to be observed, and the S / N ratio is poor in the field, and the minimum detection level is increased in many cases, which is not practical.

FIG. 11: Edited by The Institute of Electrical Engineers of Japan: "Present state and trends of preventive maintenance technology for transformers" Technical Report of the Institute of Electrical Engineers of Japan (Part II)
No. 344, August 1990, (Construction Committee for Preventive Maintenance Survey of Transformers) is a block diagram showing a conventional discharge detection method by detection of discharge noise, 27 is the inside of the target device filled with oil or the like, 28 is a tank wall of the target device, 29 is a piezoelectric element, 30 is a magnet plate, 31 is a cable, and
9 to 31 constitute an ultrasonic microphone.

This is a method in which an ultrasonic microphone is attached to the tank wall 28 of the target device to detect the discharge sound, but the sensitivity cannot be expected so much. In the field, it is difficult to remove external noise such as rain or the sound of sand particles colliding with the target device.

As another conventional example, there is a method of chemically analyzing decomposition products. This is a method in which the fluid insulation (oil or gas) in which the organic insulator is thermally decomposed and dissolved and mixed by discharge is sampled and analyzed, and it is judged from the gas component. It takes time to make the judgment, and it is necessary to have specialized knowledge and experience such as thermal decomposition characteristics of the insulator.

As a conventional example of a method for detecting an electromagnetic wave and an electromagnetic field component generated by discharge, Japanese Patent Laid-Open No. 62-1345
74 "Corona discharge detection device", JP-A-2-297078
"Abnormality detection device for electric equipment", Japanese Patent Laid-Open No. 3-81674
"Partial discharge detection device for electric equipment", JP-A-3-2399
71 There is a "corona discharge detector".

FIG. 12 is a block diagram of a corona discharge detecting device shown in Japanese Patent Laid-Open No. 62-134574 "Corona discharge detecting device". In the figure, 33 is a conductor through which a high-voltage current flows, and is fixed to a metal duct 32 via a support plate 34. Reference numeral 35 is an antenna for detecting an electromagnetic wave generated by a corona discharge generated inside the duct.
It is fixed to 2. The antenna 35 is connected to the control unit 37 by the connector 36 only at the time of inspection. Next, the operation will be described. When corona discharge occurs, electromagnetic waves are generated accordingly. By detecting the electromagnetic waves generated by the corona discharge by connecting the portable control unit to the antenna one by one and performing the detection work when the antennas installed everywhere in the duct are patrolled, the occurrence of the corona discharge is known. In this method, the antenna and the control unit are independent, so there is a drawback that discharge is not detected unless electromagnetic waves are generated when the control unit is connected to the antenna, rather than real-time detection. That is, this method is effective when insulation deterioration progresses and continuous discharge occurs,
If the discharge is generated only discretely in the initial state of insulation deterioration, the discharge may not be detected.

13 and 14 show conventional examples shown in JP-A-2-297078 "Abnormality detection device for electric equipment" and JP-A-3-81674 "Partial discharge detection device for electric equipment". In the figure, 38 is a magnetic sensor formed by winding a plurality of conducting wires around a magnetic core to detect a magnetic field component of an electromagnetic wave generated by partial discharge, and 39 is an ultrasonic wave generated by partial discharge. Sound receiver, 40 is amplifier A, 4
Reference numeral 1 is an amplifier B, 42 is a discharge detection circuit, 37 is a light receiving sensor for ultraviolet rays generated by partial discharge, and 43 is a display device. Next, the operation will be described. In FIG. 13, when a partial discharge occurs in the target device 2, electromagnetic waves and ultrasonic waves are generated accordingly. The electromagnetic wave is detected by the magnetic sensor 38 and is amplified by the amplifier A 40. The discharge detection circuit 4
Sent to 2. The ultrasonic wave is detected by the sound receiver 39, amplified by the amplifier B35, and sent to the discharge detection circuit 42. In the discharge detection circuit, when there is input from both the magnetic sensor and the sound receiver, the display device 43 is operated assuming that discharge has occurred. When input from only one of them, it is judged as a disturbance. In FIG. 14, the sound receiver is replaced with a light receiving sensor for detecting the ultraviolet rays generated by the partial discharge. This method is a method of detecting electromagnetic waves generated by partial discharge with a magnetic sensor.In order to distinguish the disturbance entering the magnetic sensor and improve the detection accuracy, other detection methods such as a sound receiver or light receiving sensor are used. The methods are used together. Therefore, since a plurality of sensors are used together, the device becomes complicated. Further, the magnetic sensor has a structure in which a winding is wound around a magnetic core, and the frequency of electromagnetic waves that can be detected by this structure is up to several MHz. Since electromagnetic waves in this frequency band have already been used for many purposes without gaps, it is difficult to avoid the disturbance from jumping into the magnetic sensor, and it is inevitable to use it together with other methods.

A conventional example shown in Japanese Patent Laid-Open No. 3-239971 "Corona discharge detector" is shown in FIG. In the figure, 4
Reference numeral 5 is a sensor unit, and 46 is a group of small loop antennas having different electromagnetic induction frequencies, and covers a frequency of 10 KHz to 1 GHz as a whole. 47 is a coaxial cable, 48 is an object to be measured, 49 is a comparison detector, 50 is a noise detection dummy antenna, 51 is CPU, 52 is RAM, 53 is ROM, 5
Reference numeral 4 is a CRT, and 55 is a printer. Next, the operation will be described. 10 KHz to 1 GHz of electromagnetic waves generated by corona discharge generated by insulation deterioration of the DUT 48
Is received by the antenna 46 and input to the comparison detector 49 through the coaxial cable 47. Further, noise in the space is received by the dummy antenna 50 and input to the comparison detector 49. The electromagnetic wave associated with the discharge is compared with noise, and a comparison output is output from the comparison detector, processed by the CPU 51, and displayed on the CRT 54 and the printer 55. This method requires a plurality of antennas to receive electromagnetic waves generated by discharge over a wide band of 10 kHz to 1 GHz. Also, since this frequency band is already used for many applications,
An external antenna for reference is required to distinguish it from external noise.

[0014]

Since the conventional discharge detection method is constructed as described above, it is vulnerable to disturbance in the field, and in order to accurately detect the discharge phenomenon, a plurality of detection methods and noise elimination devices are required. I had to use it together. Further, in the conventional method of detecting the electromagnetic wave associated with discharge, the target frequency is 1 GHz or less. The electromagnetic wave generated by the discharge has a wide-band frequency spectrum from a low frequency of several KHz to a microwave of several tens GHz as shown in FIG. 16, and its distribution is approximately 1 / f (f:
Frequency). Therefore, when the discharge is detected by the electromagnetic wave, it is efficient if the configuration is such that the low frequency electromagnetic wave is received, and there has been no configuration utilizing microwaves in the past. However, since the low frequency region uses the overcrowded range of electromagnetic waves, it has a drawback that it is easily affected by other electromagnetic waves, and therefore it is necessary to use a noise / disturbance removing device together.

(Object of the Invention) The present invention has been made in order to solve the above problems, and paying attention to the fact that the electromagnetic waves generated by discharge are in the microwave region, and the frequency components of the microwave band are The purpose of the present invention is to obtain a microwave sensor that is simple, accurate, robust against disturbances, and detects discharge in real time by extracting

[0016]

A microwave sensor according to the present invention is provided in the vicinity of an electric device, and has an antenna section for receiving a microwave signal generated by a discharge of the electric apparatus, and an antenna section for receiving the microwave signal. A first bandpass filter for passing a predetermined frequency of the microwave signal,
An amplifying means for amplifying the microwave signal output from the first bandpass filter, a second bandpass filter for removing noise generated by the amplifying means, and an output from the second bandpass filter. Converting means for converting the microwave signal into a video signal, and video amplifying means for amplifying the video signal output from the converting means,
Is provided.

Further, an antenna unit provided near the electric device for receiving a microwave signal generated by the discharge of the electric device and a first frequency unit for allowing a predetermined frequency of the microwave signal received by the antenna unit to pass therethrough. A bandpass filter, an amplification means for amplifying a microwave signal output from the first bandpass filter, a transmission means for outputting a transmission signal, a microwave signal from the amplification means and a transmission signal from the transmission means. Mixing means for forming an intermediate frequency signal by mixing them as an input signal, and a second means for removing noise of the intermediate frequency signal output from the mixing means.
Band pass filter, intermediate frequency amplification means for amplifying the intermediate frequency signal output from the second band pass filter, and conversion means for converting the intermediate frequency signal output from the intermediate frequency amplification means into a video signal. , Video amplifying means for amplifying the video signal output from the converting means.

[0018] Further, the first antenna unit is provided in the vicinity of the electric device and receives the microwave signal generated by the discharge of the electric device, and the first frequency component of the microwave signal received by the antenna unit. A bandpass filter, an amplification means for amplifying a microwave signal output from the first bandpass filter, a transmission means for outputting a transmission signal, a microwave signal from the amplification means and a transmission signal from the transmission means. Is used as an input signal to form an intermediate frequency, a second bandpass filter for removing noise of the intermediate frequency signal output from the mixing means, and a second bandpass filter Intermediate frequency amplifying means for amplifying the output intermediate frequency signal, and amplifying the intermediate frequency signal output from the second bandpass filter Comprises a logarithmic amplifier converting means for converting the video signal, a video amplifying means for amplifying the video signal output from the logarithmic amplifier converting means.

Further, a coupling means for extracting a part of the microwave signal, a comparing means for comparing the electromagnetic wave level of the microwave signal extracted by the coupling means with a predetermined value, and an attenuating means for attenuating the microwave signal. And a switching means for switching the microwave signal to the attenuating means before the amplifying means, and when the electromagnetic wave level of the microwave signal input to the comparing means exceeds a predetermined value, the switching means is changed to the attenuating means. It switches automatically.

Further, a cutoff means including a switch and a terminating device for cutting off the microwave signal when the electromagnetic wave level of the microwave signal reaches a predetermined value is provided in the preceding stage of the amplification means.

Further, a limiter for limiting the electromagnetic wave level of the microwave signal when the electromagnetic wave level of the microwave signal reaches a predetermined value is provided before the amplifying means.

[0022]

In the microwave sensor according to the present invention, a microwave signal is received among the electromagnetic waves generated by the discharge of electric equipment, and the first band pass filter receives the microwave signal at the antenna section. The predetermined frequency of the signal is passed, and the amplification means amplifies the microwave signal output from the first bandpass filter. The second bandpass filter removes noise generated by the amplifying means, the converting means converts the microwave signal output from the second bandpass filter into a video signal, and the video amplifying means outputs from the converting means. The amplified video signal is amplified. The occurrence of discharge is detected by displaying this video signal by an arbitrary observing means.

The mixing means increases the stability of the device by forming an intermediate frequency signal by mixing the microwave signal and the transmission signal from the transmission means as input signals.

Also, the logarithmic amplification conversion means expands the response range by amplifying the intermediate frequency signal and converts it into a video signal.

Further, when the electromagnetic wave level of the microwave signal inputted to the comparing means becomes equal to or more than a predetermined value, the switching means is automatically switched to the attenuating means to attenuate the microwave signal and the dynamic means of the converting means. Expand the range.

The cutoff means composed of the switch and the terminator cuts off the microwave signal when the electromagnetic wave level of the microwave signal reaches a predetermined value, and protects the present device against excessive input.

The limiter limits the electromagnetic wave level of the microwave signal when the electromagnetic wave level of the microwave signal reaches a predetermined value, and protects this device against excessive input.

[0028]

【Example】

Example 1. An embodiment of the present invention will be described below with reference to the drawings. 1 is a block diagram of a discharge detection device for electric equipment according to the present invention, FIG. 2 (a) is a block diagram, FIG. 2 (b) is a diagram showing signal and voltage level diagrams, and FIG. 2 (c) is electric equipment discharge. It is a figure which shows the input-output characteristic of a detection apparatus. In FIG.
1 is a target device case of a device that generates a discharge, 2 is a target device, 3 is an antenna attached to the target device case 1, an antenna for receiving a microwave signal generated by the discharge, 4 is connected to the antenna 3, and a microwave signal Is a signal processing unit that amplifies and detects a signal and amplifies the detected video, and 13 is an output terminal that outputs a video signal. The microwave sensor includes an antenna 3, a signal processing unit 4, and an output terminal 13. FIG. 2A is a block diagram showing the configuration of a discharge detection device for electric equipment. In the figure, 3 is an antenna for receiving a microwave signal generated by discharge, 5a is a band pass filter for a high frequency band that allows a certain frequency of the microwave signal received by the antenna to pass, and 6 is an output of the band pass filter 5a. Is a low noise amplifier for amplifying the noise, 5b is a band pass filter for a high frequency band for removing the noise of the amplifier 6, 10 is a wave detector for converting a microwave signal of the band pass filter into a video signal, and 11 is a video signal Is an output terminal for outputting a video signal.

Next, the operation will be described. 2 (a),
In (b), the microwave signal f1 (for example, 5 GHz shown in FIG. 16) having the power of P1 generated by the discharge inside the device is received by the antenna 3 and is increased to the power of P2 by the gain. Is output. This signal f1 passes through the high-frequency bandpass filter 5a and its output is reduced to P3 due to the loss of the filter, but is amplified to a predetermined level P4 by the low noise amplifier 6. Further, after passing only a necessary signal component in the bandpass filter 5b, the microwave signal is directly converted into a video signal (level V1) which is a DC signal in the detector 10, and the video amplifier 11 reaches the level of V2. It is amplified and output from the output terminal 13. The bandpass filter 5a is
Since the level of the electromagnetic wave due to the discharge is higher as the frequency is lower (see FIG. 16), f1 ± several hundred MHz (for example, f1 ± (100 MHz), and the bandpass filter 5b adds noise to the signal f1 due to the noise of the low noise amplifier 6 and is used to remove the noise. The output signal is observed by an arbitrary observation device such as an oscilloscope. On the display screen, for example, as shown in FIG. 3, the positive or negative half-wave component of the envelope of the microwave signal is displayed.

In FIG. 2B, Pmax indicates the maximum detection level in the case of Pmin which is the minimum detection level of discharge that can be received by the sensor. Although the level varies depending on the discharge form even at the same frequency, the electromagnetic wave level generated in the abnormal initial stage of the power equipment is very low −100 dBm to −8.
It is 0 dBm, and it is necessary to detect this minimum level. The intensity of discharge increases with the progress of abnormalities in electrical equipment, and the level of electromagnetic waves generated accordingly increases. Therefore, it is preferable that the dynamic range is large, but the dynamic range is limited and the maximum detection level Pmax is determined depending on the characteristics of components used (such as saturation).

The input / output characteristics of the sensor are shown in FIG. By the above operation, the video signal corresponding to the microwave signal level is output between the minimum detection level Pmin and the maximum detection level Pmax. Note that the microwave signal is not detected because the microwave signal is hidden by the noise of the sensor itself at Pmin or less because it depends on the characteristics of the semiconductor element used for the detector and the like. Also, P
Above max, the detector will be saturated, and no further video output can be obtained.

In this configuration, the receiving sensitivity is not high, but
It has sufficient sensitivity for discharges with a large electromagnetic wave level (about -80 dBm to -50 dBm) associated with radiation such as arc discharge and spark discharge, and is suitable for detection of relatively large levels.

As described above, the electromagnetic wave generated by the discharge has a wide range of frequency components from the low frequency band to the microwave band, but the electromagnetic wave below the microwave band is occupied by various electromagnetic waves such as broadcast waves and communication waves, which causes interference. It is easy to receive, but the use of microwaves is limited, the attenuation in space is large, and it is hardly affected by electromagnetic waves in space, so there is almost no noise, and noise other than discharge is considered, such as the method of using sound. You can make an accurate decision without having to.

Further, in the low frequency band, a device for removing noise electromagnetic waves, which is necessary for detecting discharge, is unnecessary, and the microwave is directly converted into the video signal by the detector, so that the circuit structure is simple and Since each part of the device is extremely small because the microwave band is used, a compact and inexpensive microwave sensor can be obtained.

Further, it becomes possible to detect the discharge in an arbitrary range by utilizing the directivity of the antenna.

Further, since each part of the device is extremely small and the non-contact type discharge detection method utilizing the directivity of the antenna, the device can be mounted without being restricted by insulation dimensions and mounting.

Furthermore, since the primary phenomenon associated with discharge is electrically detected (discharge-electromagnetic wave emission-detection), it can be performed more quickly than scientific methods (discharge-heating-organic insulator decomposition-collection-analysis-detection). It can be detected and judged easily.

Further, since the sensor is small, by providing a large number of sensors, it is possible to analyze the electromagnetic wave generation position based on the detection time difference, the level difference and the like.

Embodiment 2 FIG. Another embodiment of the present invention will be described below. In the initial state of insulation deterioration of electric power equipment, glow discharge and corona discharge are mainly, but the radiated electromagnetic wave level is small. This level of discharge must be detected for preventive maintenance of power equipment. If the receiving portion of the sensor is configured by the direct detection method of directly converting the microwave into the DC signal as in the first embodiment, the gain of the low noise amplifier 6 needs to be high gain (about 80 dB). , The amplifier easily oscillates and is difficult to detect. In this embodiment, an electromagnetic wave having a small level is detected without increasing the gain of the low noise amplifier 6. FIG. 4 is a block diagram showing the configuration of the microwave sensor. 3,
5a, 6, 10, 11, and 13 are the same as in FIG.
Since it is the same as (a), its explanation is omitted. Reference numeral 7 is a mixer for outputting an intermediate frequency signal based on the difference between the frequency of the microwave signal output from the low noise amplifier 6 and the constant frequency oscillated by the oscillator 8, and 12 is the spurious generated by the mixer 7. A bandpass filter for the intermediate frequency band to be removed, and 9 is an intermediate frequency amplifier for amplifying the output of the bandpass filter 12.

Next, the operation will be described. The microwave signal f1 generated by the discharge inside the device is received by the antenna 3. The signal f1 passes through the bandpass filter 5, is amplified to a predetermined level by the low noise amplifier 6, and is sent to the mixer 7. Also, from the output of the oscillator 8 to the frequency f
2 signal is input to the mixer 7, resulting in f3 = f
An intermediate frequency signal of 1-f2 is output from the mixer 7. For this signal f3, f2 is determined so as to have an intermediate frequency of about several hundred MHz. Next, a necessary signal is extracted from this signal by a bandpass filter 12, amplified by an intermediate frequency amplifier 9, converted into a video signal by a detector 10, and amplified by a video amplifier circuit 11.
It is output from the output terminal 13. Bandpass filter 12
When frequency conversion is performed by the mixer 7, 2f1 near f3
A spurious of -f2,2f2-f1 is generated. This spur is removed. The signal output from the output terminal is observed by an arbitrary observation device such as an oscilloscope.

When amplifying at a single frequency, the low noise amplifier must have a high gain, but if a high-gain amplifier is constructed at a single frequency, problems such as oscillation are likely to occur. However, since the frequency is converted and the amplifiers are separately provided in the high-frequency part and the intermediate-frequency part by the above configuration, the stability of the device is increased and problems such as oscillation can be avoided. Further, since the gain of the amplifier can be increased stably as the frequency is lower, the gain of the intermediate frequency amplifier 9 can be easily increased and the gain of the low noise amplifier 6 can be lowered. Therefore, it is possible to accurately detect an electromagnetic wave having a low level due to discharge, and further improve the detection performance.

Example 3. In this embodiment, the response range is expanded, and the drawings will be described. FIG. 5 is a block diagram showing the configuration of the microwave sensor. In the figure, 3,5a, 6,7,8,12,11,13 are the same as those in FIG. 4 showing the second embodiment, and the description thereof is omitted. 1
Reference numeral 4 is a logarithmic amplifier which outputs a video signal by linear-logarithmically converting and amplifying the output of the bandpass filter 12 by a logarithmic amplifier.

Next, the operation will be described. The microwave signal f1 generated by the discharge inside the device is received by the antenna 3. The signal f1 passes through the bandpass filter 5, is amplified to a predetermined level by the low noise amplifier 6, and is sent to the mixer 7. Also, from the output of the oscillator 8 to the frequency f
2 signal is input to the mixer 7, resulting in f3 = f
A signal having a frequency of 1-f2 is output from the mixer 7.
The signal f3 output from the mixer 7 passes through the band pass filter 12 in the intermediate frequency band, only the necessary signal is extracted, linearly logarithmically converted and amplified by the logarithmic amplifier 14, and then output as a video signal. It is amplified by the video amplifier 11 and output. With the above configuration, the second embodiment
In the present embodiment, 50 to 60 dB can be secured, and the difference is at least 20 d.
Since it is B, a response range of at least 100 times can be obtained.

With the above structure, the response range can be expanded and the detection performance can be further improved.

Example 4. In the present embodiment, the dynamic range of the detector of the first and second embodiments is ensured, and the drawings will be described. FIG. 6 is a block diagram from the antenna 3 of the microwave sensor to the low noise amplifier 6. In the figure, 3, 5a and 6 are the same as those in FIG. 2 showing the first embodiment, and the explanation thereof is omitted. 15 is an attenuator group 16
Is a switch for switching the microwave signal, 19 is a coupler for extracting a part of the microwave signal, 20 is a comparator for comparing the microwave signals extracted by the coupler 19, and outputting the signal to the switch 15. After the low noise amplifier, Examples 1 and 2
Is the same as

Next, the operation will be described. The microwave signal f1 generated by the discharge inside the device is received by the antenna 3. This signal f1 passes through the bandpass filter 5 and the attenuator group 16 switched by the switch 15.
The signal level is attenuated by passing through and then sent to the low noise amplifier 6. The limit of the dynamic range of the detector 10 is about 30 dB, but with the attenuator 16,
By changing the level of the detection signal and adjusting the input signal to the detector 10, for example, when the value of the attenuator is 30 dB, the dynamic range of the sensor is expanded to 60 dB. The configuration after the low noise amplifier is the same as in the first and second embodiments. The switch 15 extracts a part of the microwave signal f1 by the coupler 19, compares the microwave signal f1 with a comparator 20 and determines whether the level of the microwave signal has reached a certain level, and outputs the control from the comparator 20. It is automatically switched by a signal.

With the above configuration, the dynamic range of the detector can be expanded and the detection performance can be further improved.

Example 5. The present embodiment will be described below with reference to the drawings. FIG. 7 is a block diagram from the antenna 3 of the microwave sensor to the low noise amplifier 6. 3,
5a, 15, and 6 are the same as those in FIGS. 2 and 6, and the description thereof is omitted. Reference numeral 17 denotes a terminator to which a microwave signal is input by switching the switch 15.

Next, the operation will be described. The microwave signal f1 generated by the discharge inside the device is received by the antenna 3. This signal f1 passes through the band pass filter 5, and is sent to the low noise amplifier 6 via the switch 15. The configuration after the low noise amplifier is the same as in the first to third embodiments. The switch 15 is usually connected to the low noise amplifier 6 side. Depending on the equipment to which this sensor is attached, discharge may obviously occur depending on the usage condition of the equipment, resulting in excessive input to the sensor. At this time, the switch 15 is switched to the terminator 17 side to protect the low noise amplifier 6 from excessive input and improve the reliability of the sensor. Further, a detector for detecting the level of the microwave signal f1 by the coupler 19 and the comparator 20 is provided in the preceding stage of the switch 15 as in the case of FIG. 6 showing the embodiment 4, and an excessive signal which may destroy the low noise amplifier 6 is generated. It is also possible to automatically switch the switch 15 to the terminator 17 side when input.

With the above-mentioned structure, the present device can be protected against excessive input and reliability can be improved.

Example 6. The present embodiment will be described below with reference to the drawings. FIG. 8 is a block diagram from the antenna of the microwave sensor to the low noise amplifier. 3, 5
Since a and 6 are the same as those in FIG. 2, description thereof will be omitted. 18
Is a limiter for protecting the microwave input power.

Next, the operation will be described. The microwave signal f1 generated by the discharge inside the device is received by the antenna 3. This signal f1 passes through the bandpass filter 5,
It is sent to the low noise amplifier 6 via the limiter 18 for over-input protection. The configuration after the low noise amplifier is the first to third embodiments.
Is the same as The electromagnetic wave level entering this sensor during normal use is very small. However, a sudden phenomenon may occur in the target device to which the present sensor is attached, and an excessive electromagnetic wave may be input to the antenna 3 to destroy the electronic device of the sensor. From this sudden phenomenon, the low noise amplifier 6
In order to protect the
8 is inserted so that a signal of a certain level or higher does not enter, the low noise amplifier 6 is protected from excessive input, and the reliability of the sensor is improved.

With the above-mentioned structure, this device can be protected against excessive input and reliability can be improved.

[0054]

As described above, according to the present invention, the antenna section for receiving the microwave signal generated by the discharge of the electric device and the predetermined frequency of the microwave signal received by the antenna section are passed. A first bandpass filter, an amplifying means for amplifying a microwave signal output from the first bandpass filter, a second bandpass filter for removing noise generated by the amplifying means, and a second bandpass filter. Since the conversion means for converting the microwave signal output from the band-pass filter of 1 to the video signal and the video amplification means for amplifying the video signal output from this conversion means are provided, it is not affected by disturbance. The reliability is high and the discharge can be accurately detected. Also, since the microwave band is used, the size of the sensor body becomes small, and therefore, it is possible to locate the position by attaching a large number of sensors to the device.

Further, there are provided transmitting means for outputting the transmitting signal, and mixing means for forming an intermediate frequency signal by mixing the microwave signal from the amplifying means and the transmitting signal from the transmitting means as input signals. Therefore, the stability of the device is increased, and a discharge having a small level can be accurately detected.

Since the logarithmic amplification means for amplifying the intermediate frequency signal and converting it into the video signal is provided, the response range can be expanded and the detection performance can be further improved.

Further, when the electromagnetic wave level of the microwave signal input to the comparison means becomes equal to or higher than a predetermined value, the switching means is automatically switched to the attenuation means, so that the dynamic range of the conversion means can be expanded. Therefore, the detection performance can be further improved.

Further, since the shutoff means including the switch and the terminator for shutting off the microwave signal when the electromagnetic wave level of the microwave signal reaches a predetermined value is provided, the present apparatus is protected against excessive input. The reliability can be improved.

Further, since the limiter for limiting the electromagnetic wave level of the microwave signal when the electromagnetic wave level of the microwave signal reaches a predetermined value is provided, the present device is protected against excessive input and reliability is improved. can do.

[Brief description of drawings]

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

2A, 2B, and 2C are block diagrams showing an embodiment of the present invention.

FIG. 3 is a diagram showing an example of a display screen according to an embodiment of the present invention.

FIG. 4 is a block diagram showing another embodiment of the present invention.

FIG. 5 is a block diagram showing another embodiment of the present invention.

FIG. 6 is a block diagram showing another embodiment of the present invention.

FIG. 7 is a block diagram showing another embodiment of the present invention.

FIG. 8 is a block diagram showing another embodiment of the present invention.

FIG. 9 is a block diagram showing a conventional embodiment.

FIG. 10 is a block diagram showing a conventional embodiment.

FIG. 11 is a configuration diagram showing a conventional embodiment.

FIG. 12 is a configuration diagram showing a conventional embodiment.

FIG. 13 is a block diagram showing a conventional example.

FIG. 14 is a block diagram showing a conventional example.

FIG. 15 is a configuration diagram showing a conventional embodiment.

FIG. 16 is a characteristic diagram of a frequency spectrum of an electromagnetic wave generated due to discharge.

[Explanation of symbols]

1 target device case, 2 target device, 3 antenna, 4
Signal processor, 5a, 5b band pass filter (high frequency band), 6 low noise amplifier, 7 mixer, 8 oscillator, 9
Intermediate frequency amplifier, 10 detector, 11 video amplifier, 12 band pass filter (intermediate frequency band), 13
Video output, 14 logarithmic amplifier, 15 switches, 16
Attenuator group, 17 terminator, 18 limiter, 19 coupler, 20 comparator.

Claims (6)

[Claims] 1. An antenna unit provided in the vicinity of an electric device for receiving a microwave signal generated by discharge of the electric device, and a predetermined frequency of the microwave signal received by the antenna unit. No. 1 bandpass filter, an amplifying unit for amplifying the microwave signal output from the first bandpass filter, a second bandpass filter for removing noise generated by the amplifying unit, and a second bandpass filter. Of the microwave signal output from the band-pass filter, and a video amplifying means for amplifying the video signal output from the converting means. Sensor. 2. An antenna unit, which is provided in the vicinity of an electric device and receives a microwave signal generated by discharge of the electric device, and a predetermined frequency of the microwave signal received by the antenna unit. 1 band-pass filter, amplification means for amplifying the microwave signal output from the first band-pass filter, transmission means for outputting a transmission signal, microwave signal from the amplification means and the transmission means Mixing means for forming an intermediate frequency signal by mixing these with the transmission signal as an input signal, a second bandpass filter for removing noise of the intermediate frequency signal output from the mixing means, Intermediate frequency amplifying means for amplifying the intermediate frequency signal outputted from the second band pass filter, and an intermediate frequency amplifying means outputted from the intermediate frequency amplifying means. A microwave sensor, comprising: a conversion means for converting the intermediate frequency signal into a video signal, and a video amplification means for amplifying the video signal output from the conversion means. 3. An antenna unit provided in the vicinity of an electric device for receiving a microwave signal generated by discharge of the electric device, and a predetermined frequency of the microwave signal received by the antenna unit. 1 band-pass filter, amplification means for amplifying the microwave signal output from the first band-pass filter, transmission means for outputting a transmission signal, microwave signal from the amplification means and the transmission means Mixing means for forming an intermediate frequency by mixing them with the transmission signal as an input signal, a second band pass filter for removing noise of the intermediate frequency signal output from the mixing means, Two
Intermediate frequency amplification means for amplifying the intermediate frequency signal output from the band pass filter, and logarithmic amplification conversion means for amplifying the intermediate frequency signal output from the second band pass filter and converting the intermediate frequency signal into a video signal, A microwave sensor comprising: a video amplification means for amplifying the video signal output from the logarithmic amplification conversion means. 4. A combining means for extracting a part of the microwave signal, a comparing means for comparing an electromagnetic wave level of the microwave signal extracted by the combining means with a predetermined value, and an attenuation of the microwave signal. Attenuating means for switching and a switching means for switching the microwave signal to the attenuating means are provided in the preceding stage of the amplifying means, and when the electromagnetic wave level of the microwave signal input to the comparing means exceeds a predetermined value. 3. The microwave sensor according to claim 1, wherein the switching means is automatically switched to the attenuation means. 5. A blocking means comprising a switching device and a terminating device for blocking the microwave signal when the electromagnetic wave level of the microwave signal reaches a predetermined value, is provided in front of the amplifying means. The microwave sensor according to claim 1 or 2. 6. A limiter for limiting the electromagnetic wave level of the microwave signal when the electromagnetic wave level of the microwave signal reaches a predetermined value, is provided in the preceding stage of the amplifying means. Alternatively, the microwave sensor described in 2.