KR101496442B1 - Partial discharge diagnosis device for the cable - Google Patents

Abstract

The present invention relates to a cable partial discharge diagnosis apparatus. The cable partial discharge diagnosis apparatus includes a detection sensor for detecting a partial discharge signal of the cable; A band-pass filter for filtering the noise of the detection sensor; An amplifier for amplifying an output signal of the band-pass filter; A frequency tuning filter for tuning the frequency of the output signal of the amplifier; An envelope detector for measuring the length and shape of the output signal of the frequency tuning filter; A peak detector for measuring the magnitude of the output signal of the envelope detector; And an analog-to-digital converter for converting the output signal of the peak detector into a digital signal. In this embodiment of the present invention, the noise and the actual partial discharge signal can be distinguished accurately and reliably at a low cost.

Description

[0001] The present invention relates to a cable partial discharge diagnostic device,

The present invention relates to a partial discharge measurement technique in the cable deterioration diagnosis method. Basically, the partial discharge generated in the underground cable is measured by mixing various noise signals. For accurate measurement and diagnosis, it is important to distinguish between noise and partial discharge signals. The present invention relates to a technology for efficiently distinguishing a noise signal and a partial discharge signal from a measured signal by mixing an external noise signal and a PD (Partial Discharge) signal generated in a cable, and extending a measurable frequency band.

Generally, as the industry develops today, power use is increasing. In addition, facilities are becoming larger and demanding higher reliability. Therefore, stabilization of the electrical equipment is a very important task. In particular, high reliability of electricity supply is an essential element of industrial society. The power supply method can be divided into working cable and underground cable. In urban area, it is gradually changed into underground cable due to aesthetic and installation conditions.

However, it is best to prevent underground cables before an accident occurs because it takes a long time to recover when an accident occurs.

Deterioration test methods to prevent underground cable accidents are diagonal deterioration diagnosis method and live wire deterioration diagnosis method.

The use of the oblique deterioration diagnosis method is very limited because the power must be cut off for the deterioration judgment. On the other hand, the on-line deterioration diagnosis method is a very efficient method since it can be measured even in the live state of the underground cable.

Deterioration diagnosis devices in use in Korea can be roughly divided into DC superposition method, DC component method, dielectric tangent method, and partial discharge measurement method.

In the partial discharge diagnosis method, when a partial discharge occurs in an underground cable, measurement is performed using various sensors, and a signal from the sensor is analyzed to determine a partial discharge.

However, various noise signals are mixed and measured in the signal output from the sensor for the fractional discharge measurement. For accurate measurement and diagnosis, it is important to distinguish between noise and partial discharge signals.

Conventionally, two measurement techniques have been used for partial discharge measurement of a power cable.

First, it is PRPDA (Phase Resolved Peak Detect Analysis) technology that can adjust the frequency.

In this method, a frequency-adjustable signal and a partial discharge signal are synthesized through a mixer, a synthesized signal is passed through a narrow-band filter, and a peak value is detected using a peak detector. It is similar to the way to adjust the frequency in the FM radio to pick up the signal. Although this method can detect the magnitude and frequency of the partial discharge, it only detects the peak value. Therefore, it is difficult to distinguish the two signals when the noise and the partial discharge signal are mixed.

In addition, there is a method using a high-speed ADC (Analog Digital Converter) as an analysis method of the partial discharge signal.

This method can digitally convert the signal itself and perform frequency analysis through Fourier transform, which is the most reliable method. However, the partial discharge signal Because the frequency is very high, it is necessary to use an analog-to-digital converter (ADC) that is above Giga sampling, but because the price of the equipment is too high to use analog-to-digital conversion of Giga sampling, existing devices may require hundreds of mega- ) Analog digital converters and choosing a method to reduce the maximum measurement frequency range to several tens of MHz.

Since the conventional cable partial discharge diagnostic products detect only the peak value, it is difficult to distinguish between the noise and the actual partial discharge signal, or it is possible to directly analyze and digitize the signal. However, due to the limit of the analog digital converter The frequency band that can be measured is narrow.

SUMMARY OF THE INVENTION The present invention has been made in an effort to solve the conventional disadvantages, and it is an object of the present invention to provide a cable partial discharge diagnostic apparatus which can accurately and reliably distinguish noise and actual partial discharge signals and extend a measurable frequency band.

In order to solve such a problem, a cable partial discharge diagnosis apparatus according to a feature of the present invention comprises:

A sensing sensor for sensing a partial discharge signal of the cable;

A band-pass filter for filtering the noise of the detection sensor;

An amplifier for amplifying an output signal of the band-pass filter;

A frequency tuning filter for tuning the frequency of the output signal of the amplifier;

An envelope detector for measuring the length and shape of the output signal of the frequency tuning filter;

A peak detector for measuring the magnitude of the output signal of the envelope detector;

And an analog-to-digital converter for converting the output signal of the peak detector into a digital signal.

The apparatus comprises:

A partial discharge signal detector for identifying the noise and the PD by checking the length and shape of the output signal of the analog digital signal converter;

And a partial discharge pattern analyzing unit for verifying the type of the partial discharge through the PRPD mapping of the output signal of the partial discharge signal detecting unit.

The detection sensor is an HF sensor or an HF CT sensor. The measurement range of the HF sensor is 5 MHz to 200 MHz, and the measurement range of the HFCT sensor is 1 MHz to 100 MHz.

And the band-pass filter is a band-pass filter having a pass band of 1 MHz to 200 MHz.

Wherein the frequency tuning filter comprises:

A signal generator for generating a signal having a frequency of 200 MHz to 420 MHz;

A mixer for mixing a signal having passed through the amplifier and a signal generated from the signal generator together to output a signal having a frequency corresponding to a sum of the output signal of the amplifier and the signal generator output signal;

And a narrowband bandpass filter for filtering the output signals of the mixer into a narrow band having a center frequency of 425 MHz and a bandwidth of 20 MHz.

According to another aspect of the present invention, there is provided a cable partial discharge diagnosis apparatus comprising:

A cable partial discharge diagnostic apparatus for diagnosing a partial discharge of a cable by receiving an output signal of a detection sensor for detecting a partial discharge signal of a cable buried in an underground,

A band-pass filter for filtering the noise of the detection sensor;

An amplifier for amplifying an output signal of the band-pass filter;

A frequency tuning filter for tuning the frequency of the output signal of the amplifier;

An envelope detector for measuring the length and shape of the output signal of the frequency tuning filter;

A peak detector for measuring the magnitude of the output signal of the envelope detector;

And an analog-to-digital converter for converting the output signal of the peak detector into a digital signal.

According to another aspect of the present invention, there is provided a cable partial discharge diagnosis apparatus comprising:

A cable partial discharge diagnostic apparatus for diagnosing a partial discharge of a cable by receiving an output signal of a detection sensor for detecting a partial discharge signal of a cable buried in an underground,

A band-pass filter for filtering the noise of the detection sensor;

An amplifier for amplifying an output signal of the band-pass filter;

A frequency tuning filter for tuning the frequency of the output signal of the amplifier;

An envelope detector for measuring the length and shape of the output signal of the frequency tuning filter;

And a high-speed analog-to-digital converter for converting an output signal of the envelope detector into a digital signal.

In the embodiment of the present invention, it is possible to provide a cable partial discharge diagnostic apparatus capable of distinguishing noise and actual partial discharge signals accurately and reliably at a small cost and extending a measurable partial discharge frequency band.

1 is a configuration diagram of a cable partial discharge diagnosis apparatus according to an embodiment of the present invention.
2 is a diagram illustrating a configuration of a frequency tuning filter in a cable partial discharge diagnosis apparatus according to an embodiment of the present invention.
3 is a diagram showing the configuration of an envelope detector in a cable partial discharge diagnosis apparatus according to an embodiment of the present invention.
4 to 9 are waveform diagrams of parts of a cable partial discharge diagnosis apparatus according to an embodiment of the present invention.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those skilled in the art can easily carry out the present invention. The present invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. In order to clearly illustrate the present invention, parts not related to the description are omitted, and similar parts are denoted by like reference characters throughout the specification.

1 is a configuration diagram of a cable partial discharge diagnosis apparatus according to an embodiment of the present invention.

Referring to FIG. 1, a cable partial discharge diagnosis apparatus according to an embodiment of the present invention includes:

A bandpass filter 210 for primarily filtering the noise, an amplifier 220 for amplifying the acquired signal, a frequency tuning filter 230 for frequency measurement of the acquired signal, ), An envelope detector 240 for measuring the length and shape of the signal, a peak detector 250 for size measurement, analogue digital converters 260 and 270, and the length and shape of the signal to discriminate between noise and PD And a partial discharge pattern analyzer 320 for verifying the type of partial discharge through the PRPD mapping.

The sensing sensor 100 may be an HF sensor, an HF CT sensor, or the like. In the case of the HF sensor, the measurement range is 5 MHz to 200 MHz. In the case of the HFCT sensor, the measurement range is 1 MHz to 100 MHz.

The bandpass filter 210 is a bandpass filter having a passband of 1 MHz to 200 MHz and is a passive filter composed of a chip ceramic inductor and a chip ceramic capacitor. It plays a role of letting only the frequency of the required band among the signals acquired by the sensor pass, and thereby eliminates the noise in the first place.

The amplifier 220 is an RF amplifier, which amplifies the output waveform of the bandpass filter to effectively perform signal processing. Basically, the signal measured on the cable is very small, making it difficult to process the signal. Since the signal passes through the band-pass filter and attenuates slightly, the RF amplifier amplifies the waveform and effectively processes the signal.

Referring to FIG. 2, the frequency tuning filter 230 includes a signal generator 231, a mixer 232, and a narrowband bandpass filter 233. The RF signal passed through the amplifier 220 passes through the mixer 232 together with a local oscillator (LO) signal generated by the signal generator 231. The signal passed through the mixer passes through a narrowband bandpass filter 233 having a center frequency of 425 MHz and a bandwidth of 20 MHz to acquire only necessary signals.

It can be seen that the RF signal is present in this band because it has passed through the 1MHz to 200MHz bandpass filter. If the signal of 415MHz ~ 435MHz is output through the frequency adjustment of the LO signal using the characteristics of the mixer, It is possible to pass through the filter 233 so that the frequency of occurrence of the RF signal can be found within an error range of 20 MHz. (425MHz - LO frequency = partial discharge frequency)

The envelope detector 240 detects an envelope for a signal that has passed through the narrowband bandpass filter 233 of the frequency tuning filter. This envelope detection process is similar to the process of demodulating the AM signal. Partial discharge and noise signals are clearly different on the time axis, and in particular, the partial discharge signal reaches a peak value in a very short time on the time axis and decreases rapidly, and the noise signal is elongated. By using this difference, it becomes possible to effectively distinguish between noise and partial discharge.

Referring to FIG. 3, an envelope detector 240 implemented through a diode D and an LPF (LOW PASS FILTER) is shown.

The envelope detector 240 charges the capacitor C up to the maximum value of the input signal when the input signal has a positive value. When the input signal becomes smaller than the maximum value, the diode D is turned off and the capacitor C is slowly discharged through the resistor R. In this way, every time the input signal becomes positive, the capacitor C charges the envelope to the maximum value of the input signal, and the envelope of the signal is detected by maintaining the charged voltage due to the slow discharge until the next positive value appears .

The envelope detection is not limited to the above-described configuration. In another embodiment, a method of suppressing signal attenuation as much as possible is to use one or more log amp ICs or a combination of BJTs, MOSFETs, and capacitors It is also possible.

The peak detector 250 is used to know the maximum size of the output signal of the frequency tuning filter 230. The envelope can be obtained through the envelope detection and analog-to-digital converter 270, but there is a possibility that the maximum value of the partial discharge and the noise signal can not be detected in the envelope detection and analog-digital conversion process. Therefore, a peak detector 250 can be additionally used to know the maximum size of the signal. The peak detector 250 draws a curve that only transitions the peak value of the original signal. This transition curve is a low-frequency signal in units of several tens kHz. The low frequency signal maintains a peak value at the peak detector.

The analog-to-digital converter 260 converts the peak hold signal into a digital signal. When the conversion is completed in the analog-to-digital converter 260, the digital signal processor (MCU) gives a reset signal to the peak reset circuit to reset the peak-held signal by the peak reset circuit so that the next peak value can be detected.

Conventional cable partial discharge diagnostic products directly analog-digital converted the signal measured by the sensor through the bandpass filter only. Because the frequency is very high, it is necessary to use an analog-to-digital converter (ADC) that is above Giga sampling, but because the price of the equipment is too high to use analog-to-digital conversion of Giga sampling, existing devices may require hundreds of mega- ) Analog digital converters and choosing a method to reduce the maximum measurement frequency range to several tens of MHz.

However, in the embodiment of the present invention, even if the same analog-to-digital converter is used by employing the envelope detection technology, measurement can be performed up to several hundreds of MHz, so that the frequency range can be expanded.

In the embodiment of the present invention, the analog-to-digital converter to be used for the output signal of the envelope detection circuit is an analog-to-digital converter within a minimum of 100M SPS to a maximum of 300M SPS.

The pulse shape analysis and partial discharge signal detector 310 analyzes the analog-to-digital converted signal passed through the envelope detector 240 and uses a predetermined analysis technique as a part for distinguishing noise from partial discharge.

When the envelope of the noise and the partial discharge signal is obtained, the pulse shape analysis and partial discharge signal detecting unit 310 distinguishes the characteristics clearly on the time axis. Therefore, the analysis is performed in the MCU using this characteristic, Or MMI or the like. The pulse shape analysis and partial discharge signal detection unit can be configured in a separate external MCU by software or hardware.

Pulse shape analysis may not know the exact size of the signal. Therefore, this technique is used to analyze the distinction between noise and PD and the distortion characteristics of PD signals. Thus, the distinction is made between the PD and the noise signal.

The partial discharge pattern analyzing unit 320 can also be configured in a separate external MCU by software or hardware.

One of the characteristics of the partial discharge is that it occurs synchronously with the phase voltage frequency. That is, the partial discharge caused by an abnormal defect in the cable occurs in a constant pattern for each phase in phase of the phase voltage frequency. The mapping method using this pattern is the PRPD mapping. Partial Discharge Pattern Analysis The unit analyzes the pattern of partial discharge using PRPD mapping.

 The analog-to-digital converted signal through the peak detection circuit performs a Phase Resolved Peak Detect (PRPD) mapping in synchronization with the phase voltage frequency. The PRPD mapping is a method of graphically displaying peak values accumulated in real time in a fixed phase.

The operation of the cable partial discharge diagnostic apparatus according to the embodiment of the present invention having such a configuration will now be described.

A signal relating to a noise or a partial discharge is detected and output from the detection sensor 100 installed in a main portion of the cable where a partial discharge takes place. The cable partial discharge diagnosis is performed by using HF sensor, HF CT sensor or the like. In case of HF sensor, the measurement range is from 1 MHz to 100 MHz for a 5 MHz to 200 MHz HFCT sensor.

An output signal sensed by the sensing sensor 100 is input to the band-pass filter 210, and only a signal having a frequency of 1 MHz to 200 MHz, which is a band required for detecting a partial discharge, is passed through the band-pass filter 210. Thus, if the measurement range of the sensor exceeds this bandpass filter band, the primary noise that may be introduced is eliminated.

The noise-canceled signal is input to the amplifier 220 and amplified. Basically, the signal measured on the cable is very small, which makes it difficult to perform signal processing. Since the signal passes through the band-pass filter 210 and attenuates a little, the RF amplifier amplifies the waveform and effectively processes the signal. .

Next, the signal passed through the amplifier 220 is processed by a frequency tuning filter 230. The RF signal having passed through the amplifier passes through the mixer 232 together with a local oscillator (LO) signal generated by the signal generator 231. The signal generator 231 has a signal generating band of 200 MHz to 420 MHz and passes through a mixer 232 and then passes through a narrowband bandpass filter 233 having a center frequency of 425 MHz and a bandwidth of 20 MHz to acquire only a signal corresponding to the frequency sum of the two signals do. It can be seen that the RF signal is present within this band because it has passed through the 1MHz to 200MHz band pass filter. If the signal between 415MHz and 435MHz is outputted through the frequency adjustment of the LO signal using the characteristics of the mixer, It is possible to pass through the filter 233 so that the frequency of occurrence of the RF signal can be found within an error range of 20 MHz. (425 MHz-LO frequency = partial discharge frequency) The frequency tuning filter is not limited to the above-described configuration, and it may be constituted by a narrow band filter capable of adjusting the pass band.

When the original partial discharge (PD) signal is applied to the frequency tuning filter 230, the waveform shown in FIG. 4 is obtained. In the case of the noise signal, the waveform shown in FIG.

Referring to FIG. 4 or 5, when the noise signal is passed through the bandpass filter 210 and the frequency tuning filter 230, the noise signal becomes a signal that is delayed on the time axis (x axis) in comparison with the partial discharge signal.

The envelope detector 240 detects an envelope for a signal that has passed through the narrowband bandpass filter of the frequency tuning filter 230. The unprocessed partial discharge signal and the noise signal have a frequency increase due to the synthesis with the LO frequency through the frequency tuning filter. Therefore, the frequency synthesized through the envelope detector 240 is removed and the frequency of the original signal is lower than that of the original signal while maintaining the characteristics of the original signal, thereby facilitating signal processing. This envelope detection process is similar to the process of demodulating the AM signal.

For example, in Fig. 3, when the input signal has a positive value, the capacitor C is charged up to the maximum value of the input signal. When the input signal becomes smaller than the maximum value, the diode D is turned off and the capacitor C is slowly discharged through the resistor R. In this way, every time the input signal becomes positive, the capacitor C charges the envelope to the maximum value of the input signal, and the envelope of the signal is detected by maintaining the charged voltage due to the slow discharge until the next positive value appears .

The envelope detection is not limited to the above-described configuration. In another embodiment, a method of suppressing signal attenuation as much as possible is to use one or more log amp ICs or a combination of BJTs, MOSFETs, and capacitors It is also possible.

Fig. 6 is a diagram showing a waveform after the envelope detection of the partial discharge signal, and Fig. 7 is a diagram showing the waveform after envelope detection of the noise signal. Through the envelope detection, the frequency can be lowered to facilitate signal processing while maintaining the characteristics of the signal.

Referring to FIG. 6 or 7, the partial discharge and the noise signal are distinctly different on the time axis. Particularly, the partial discharge signal reaches a peak value in a very short time on the time axis and rapidly decreases. By using this difference, it becomes possible to effectively distinguish between noise and partial discharge.

The output signal of the envelope detector 240 is used as the input of the peak detector 250 and the middle-speed analog-to-digital converter 260 and as the input of the high-speed analog-to-digital converter 270.

 First, the role of the peak detector 250 will be described. Envelope detection and analog-to-digital conversion can obtain the envelope, but there is a possibility that the maximum value of the partial discharge and the noise signal can not be detected during the analog-digital conversion process of the envelope. Therefore, the peak detector 250 is additionally used so that the maximum size of the signal can be known. The peak detector 250 draws a curve that only transitions the peak value of the input signal. This transition curve is a low-frequency signal in units of several tens kHz. The low frequency signal maintains a peak value at the peak detector 250.

The mid-speed analog-to-digital converter 260 converts the peak hold signal into a digital signal. When the conversion is completed in the intermediate-to-digital analog converter 260, a reset signal is given to a peak reset circuit in a digital signal processing unit (MCU, not shown) to reset a peak-held signal by a peak reset circuit to detect a next peak value . Such a digital signal processor and a peak reset circuit are well known in the art, and detailed description thereof is omitted.

Conventional cable partial discharge diagnostic products directly analog-digital converted the signal measured by the sensor through the bandpass filter only. Because the frequency is very high, it is necessary to use an analog-to-digital converter (ADC) that is above Giga sampling, but because the price of the equipment is too high to use analog-to-digital conversion of Giga sampling, existing devices may require hundreds of mega- ) Analog digital converters and choosing a method to reduce the maximum measurement frequency range to several tens of MHz.

However, in the embodiment of the present invention, the envelope detection technique can be used to reduce the frequency while maintaining the characteristics of the signal, and to measure it up to several hundreds of MHz even using the same analog-to-digital converter.

In the embodiment of the present invention, the high-speed analog-to-digital converter 270 to be used for the output signal of the envelope detection circuit is an analog-to-digital converter within a minimum of 100M SPS to a maximum of 300M SPS.

The left side of FIG. 8 is sampled by the analog-to-digital converter 260 of the partial discharge signal. The small arrows below indicate sampling and the large arrows above indicate peak detection. The right side is the sampling and peak detection of the noise signal. As described in the above process, the transition curve indicated by the output of the peak detector 250 is a low frequency signal in units of several tens kHz. Thus, the analog to digital conversion of the signal of the peak detector 250 can be implemented with an analog to digital converter of several M sampling (SPS).

 The pulse shape analysis and partial discharge signal detector 310 analyzes the analog-to-digital converted signal passed through the envelope detector 240 and uses a predetermined analysis technique as a part for distinguishing the noise from the partial discharge signal.

When the envelope of the noise and the partial discharge signal is obtained, the pulse shape analysis and partial discharge signal detecting unit 310 distinguishes the characteristics clearly on the time axis. Therefore, the analysis is performed in the MCU using this characteristic, Or MMI or the like. The pulse shape analysis and partial discharge signal detection unit 310 can be configured in a separate external MCU by software or hardware.

Pulse shape analysis may not know the exact size of the signal. Therefore, this technique is used to analyze the distinction between noise and partial discharge signals and the distortion characteristics of partial discharge signals. Thus, the distinction between the partial discharge signal and the noise signal is performed.

The partial discharge pattern analyzing unit 320 can also be configured in a separate external MCU by software or hardware.

One of the characteristics of the partial discharge is that it occurs synchronously with the phase voltage frequency. That is, the partial discharge caused by an abnormal defect in the cable occurs in a constant pattern for each phase in phase of the phase voltage frequency. The mapping method using this pattern is the PRPD mapping. The partial discharge pattern analyzer 320 analyzes the partial discharge pattern using the PRPD mapping.

The analog-to-digital converted signal passing through the peak detector 250 performs phase resolved peak detection (PRPD) mapping in synchronization with the phase voltage frequency. The PRPD mapping is a method of graphically displaying peak values accumulated in real time in a fixed phase.

9 is a typical PRPD graph in which a PD signal synchronized with a phase voltage of 60 Hz is accumulated every cycle. Due to the characteristics of the partial discharge, the PRPD mapping shows a positive peak at 60 Hz and a phase difference of 180 at near the peak. In the embodiment of the present invention, the MCU has a function of displaying the partial discharge type through an algorithm for analyzing the partial discharge type.

The mapping result of this PRPD is also displayed on the LCD of the device in a graph similar to the above graph so that the user can confirm it.

In the embodiment of the present invention, it is possible to fabricate up to analog digital converters 260 and 270 as a single device, and if necessary, the shape analysis partial discharge signal detection unit 310 implemented in the external MCU part and the partial discharge pattern analysis (320). ≪ / RTI >

As described above, according to the embodiment of the present invention, since the frequency tuning filter is used, the frequency of the partial discharge signal can be checked, and the measurable frequency band can be extended by the analog switch of the same specification using the envelope detection. That is, there is an economic effect of providing a high specification at the same price.

In addition, pulse shape analysis is possible and effective noise discrimination and elimination are possible.

In addition, it is possible to perform pulse shape analysis as a result of envelope detection, to analyze the shape of the waveform, to perform primary noise removal and PD detection, and to perform PD type and pattern analysis through PRPD analysis of the finally detected PD signal.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the invention is not limited to the disclosed exemplary embodiments, It belongs to the scope of right.

Claims (7)

A sensing sensor for sensing a partial discharge signal of the cable;
A band-pass filter for filtering the noise of the detection sensor;
An amplifier for amplifying an output signal of the band-pass filter;
A frequency tuning filter for tuning the frequency of the output signal of the amplifier;
An envelope detector for measuring the length and shape of the output signal of the frequency tuning filter;
A peak detector for measuring the magnitude of the output signal of the envelope detector;
And an analog digital signal converter for converting an output signal of the peak detector into a digital signal,
A partial discharge signal detector for identifying the noise and the PD by checking the length and shape of the output signal of the analog digital signal converter;
And a partial discharge pattern analyzing unit for verifying the type of the partial discharge through PRPD mapping of the output signal of the partial discharge signal detecting unit,
The detection sensor is an HF sensor or an HF CT sensor. The measurement range of the HF sensor is 5 MHz to 200 MHz, and the measurement range of the HFCT sensor is 1 MHz to 100 MHz.
Wherein the band-pass filter is a band-pass filter having a pass band of 1 MHz to 200 MHz,
Wherein the frequency tuning filter comprises:
A signal generator for generating a signal having a frequency of 200 MHz to 420 MHz;
A mixer for mixing a signal having passed through the amplifier and a signal generated from the signal generator together to output a signal having a frequency corresponding to a sum of an output signal of the amplifier and an output signal of the signal generator;
And a narrowband bandpass filter for filtering the output signals of the mixer into a narrow band having a center frequency of 425 MHz and a bandwidth of 20 MHz.
delete delete delete delete A cable partial discharge diagnostic apparatus for diagnosing a partial discharge of a cable by receiving an output signal of a detection sensor for detecting a partial discharge signal of a cable buried in an underground,
A band-pass filter for filtering the noise of the detection sensor;
An amplifier for amplifying an output signal of the band-pass filter;
A frequency tuning filter for tuning the frequency of the output signal of the amplifier;
An envelope detector for measuring the length and shape of the output signal of the frequency tuning filter;
A peak detector for measuring the magnitude of the output signal of the envelope detector;
And an analog digital signal converter for converting an output signal of the peak detector into a digital signal,
Wherein the frequency tuning filter comprises:
A signal generator for generating a signal having a frequency of 200 MHz to 420 MHz;
A mixer for mixing a signal having passed through the amplifier and a signal generated from the signal generator together to output a signal having a frequency corresponding to a sum of an output signal of the amplifier and an output signal of the signal generator;
And a narrowband bandpass filter for filtering the output signals of the mixer into a narrow band having a center frequency of 425 MHz and a bandwidth of 20 MHz.
A cable partial discharge diagnostic apparatus for diagnosing a partial discharge of a cable by receiving an output signal of a detection sensor for detecting a partial discharge signal of a cable buried in an underground,
A band-pass filter for filtering the noise of the detection sensor;
An amplifier for amplifying an output signal of the band-pass filter;
A frequency tuning filter for tuning the frequency of the output signal of the amplifier;
An envelope detector for measuring the length and shape of the output signal of the frequency tuning filter;
And a high-speed analog-to-digital converter for converting an output signal of the envelope detector into a digital signal,
Wherein the frequency tuning filter comprises:
A signal generator for generating a signal having a frequency of 200 MHz to 420 MHz;
A mixer for mixing a signal having passed through the amplifier and a signal generated from the signal generator together to output a signal having a frequency corresponding to a sum of an output signal of the amplifier and an output signal of the signal generator;
And a narrowband bandpass filter for filtering the output signals of the mixer into a narrow band having a center frequency of 425 MHz and a bandwidth of 20 MHz.

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