JPH0921842A - Device and method for detecting internal partial-discharge of capacitive instrument transformer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To surely detect partial discharge inside a transformer for a capacitive instrument by surely detecting existence of a pulse current due to the internal partial-discharge of a transformer for a capacitive instrument in operation. SOLUTION: A current flowing through a grounding conductor 2 of a transformer 1 for a capacitive instrument is detected by a clamp CT3 to obtain envelope data of the frequency spectrum of an output signal Vs. Existence of an internal partial-discharge is detected by a correlation between standard envelope data obtained when an internal partial-discharge is deliberately generated for the purpose of comparison and envelope data obtained at the time of measurement.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a device and method for detecting an internal partial discharge of a transformer for a capacitive meter.

[0002]

2. Description of the Related Art Generally, when an insulator inside a power device contains voids and other weak points of withstand voltage, partial discharge (corona) occurs inside the void during operation, which causes insulation deterioration. It may lead to destruction accidents.
Conventionally, a partial discharge measuring circuit has been used to measure the partial discharge generated in the electric power equipment.

Here, an example of a conventional partial discharge measuring circuit is shown in FIG.
0 is shown. In FIG. 10, the control unit 31 is composed of a voltage regulator, an insulation transformer, a noise component removal filter, and the like, and supplies a primary voltage to the test high-voltage transformer 32. The test high voltage transformer 32 steps up this. The capacitor Cx, the coupling capacitor Ck, and the high-frequency transformer 33, which are the objects to be measured, are connected to the secondary side of the test high-voltage transformer. When partial discharge occurs in the capacitor Cx, a partial discharge pulse voltage is generated on the secondary side of the high frequency transformer connected through the coupling capacitor Ck.

Using such a partial discharge measuring circuit, the partial discharge pulse voltage is amplified, an elliptic Lissajous figure is drawn on an oscilloscope, and the pulse is drawn to observe the partial discharge.

[0005]

By the way, in a transformer for a capacitance type instrument, the high-voltage side capacitor is usually composed of a large number of capacitor elements connected in series in order to secure the withstand voltage of the high-voltage side capacitor. Partial discharge occurs due to insulation deterioration. When such insulation deterioration of one element leads to dielectric breakdown, the applied voltage to the other capacitor elements rises, and the dielectric breakdown of the capacitor elements expands in a chain. Therefore, in the transformer for a capacitance meter, it is necessary to surely detect partial discharge due to insulation deterioration of one capacitor element of the high-voltage side capacitor to prevent dielectric breakdown.

However, the conventional partial discharge measuring circuit described above cannot be applied to an object to be measured in an operating state like a transformer for a normal capacitance type instrument, and a transformer for a capacitance type instrument. Since the device is composed of a capacitor voltage divider, it has a low impedance via a high frequency component, and a high frequency current superimposed on the power system flows through its ground line. Therefore, even if we try to detect a partial discharge pulse signal from the current that flows in the ground wire of the transformer for a capacitive instrument, it is possible to directly detect the presence or absence of a pulse current due to a partial discharge inside the transformer for a capacitive instrument. It was difficult to judge.

An object of the present invention is to reliably detect the presence or absence of a pulse current due to an internal partial discharge of a transformer for a capacity type instrument in an operating state, and to reliably detect a partial discharge inside the transformer for a capacity type instrument. An apparatus and method therefor.

[0008]

According to a first aspect of the present invention, there is provided an internal partial discharge detection device for a transformer for a capacitance type instrument, comprising: a current transformer for detecting a current flowing through a ground wire of the transformer for the capacitance type instrument; Frequency spectrum extracting means for extracting the frequency spectrum of the output signal of the current transformer, envelope data generating means for obtaining the envelope data of the frequency spectrum extracted by the frequency spectrum extracting means, and the transformer for the capacitive instrument for comparison. Reference envelope data storage means for storing the envelope data obtained by the envelope data generation means as reference envelope data in a state in which partial discharge is generated inside the container,
Measurement envelope data temporary storage means for temporarily storing the envelope data obtained by the envelope data generation means at the time of measurement as measurement envelope data, and obtaining the correlation coefficient between the reference envelope data and the measurement envelope data. Correlation coefficient calculation means is provided. With this configuration, the current transformer detects the current flowing in the grounding wire of the transformer for the capacitive instrument, the frequency spectrum extracting means extracts the frequency spectrum of the output signal of the current transformer, and the envelope data generating means uses the frequency spectrum. Obtain the envelope data of the spectrum. The reference envelope data storage means stores the envelope data obtained by the envelope data generation means as reference envelope data in a state in which a partial discharge is intentionally generated inside the transformer for a capacitive instrument for comparison. The measurement envelope data temporary storage means temporarily stores the envelope data obtained by the envelope data generation means at the time of actual measurement as measurement envelope data. Then, the correlation coefficient calculating means obtains the correlation coefficient between the measurement envelope data and the reference envelope data.

As described above, in a transformer for a capacitance type instrument, partial discharge occurs due to insulation deterioration of any one of a plurality of capacitor elements forming a high-voltage side capacitor. Therefore, when internal partial discharge occurs, The envelope data of the frequency spectrum of the current signal flowing through the ground wire of the transformer for a capacitive meter is constant regardless of the location of partial discharge in the high-voltage side capacitor. Therefore, it is possible to know whether or not the internal partial discharge of the transformer for the capacitive meter is detected according to the correlation coefficient between the measured envelope data and the reference envelope data.

According to a second aspect of the present invention, there is provided the internal partial discharge detecting device for a transformer for a capacitive instrument according to the first aspect, wherein the frequency spectrum extracting means has a primary side input voltage waveform of the transformer for a capacitive instrument. The frequency spectrum is extracted from the output signal of the current transformer at a certain time in the positive or negative voltage rising process of.

According to a third aspect of the present invention, there is provided an internal partial discharge detecting device for a transformer for a capacitance type instrument according to the first or second aspect, wherein the frequency spectrum extracted by the frequency spectrum extracting means is used to detect broadcast waves, communication waves and the like. Further, frequency spectrum correction means for correcting the fluctuation component of the frequency spectrum due to artificial external noise is further provided.

According to a fourth aspect of the present invention, there is provided an internal partial discharge detecting device for a transformer for a capacitance type instrument according to the first, second or third aspect, wherein the correlation coefficient obtained by the correlation coefficient calculating means is predetermined. A detection condition determining means for determining whether or not it is greater than a value as a detection condition for detecting the presence or absence of internal partial discharge of the transformer for a capacitive instrument, and when the detection condition determining means determines that the detection condition is satisfied, And a notification unit for notifying that the internal partial discharge has occurred in the transformer for the capacitive instrument.

According to a fifth aspect of the present invention, there is provided an internal partial discharge detecting device for a transformer for a capacitive instrument according to the first, second or third aspect, wherein the level of the measurement envelope data is larger than a predetermined value, and Detection condition determination means for determining whether or not the correlation coefficient obtained by the correlation coefficient calculation means is larger than a predetermined value as a detection condition for the presence or absence of internal partial discharge of the transformer for the capacitive instrument, and the detection condition determination means. When the condition determination means determines that the detection condition is satisfied, it further comprises an informing means for informing that the internal partial discharge has occurred in the transformer for the capacitive instrument.

According to a sixth aspect of the present invention, there is provided a method for detecting an internal partial discharge of a transformer for a capacity type instrument, for the purpose of comparison. The current flowing in the ground wire is detected, the frequency spectrum of the current signal is extracted, the envelope data of the frequency spectrum is obtained as the reference envelope data, and the current flowing in the ground wire of the transformer for the capacitive instrument is measured at the time of measurement. Detect and
The frequency spectrum of the current signal is extracted, the envelope data of the frequency spectrum is obtained as the measurement envelope data, and the reference envelope data and the measurement envelope data are compared to obtain the internal portion of the transformer for the capacitive instrument. The feature is that the presence or absence of discharge is detected.

According to a seventh aspect of the present invention, there is provided a method for detecting an internal partial discharge of a transformer for a capacity type instrument, for the purpose of comparison, a transformer for a capacity type instrument is used in which a partial discharge is generated inside the transformer for a capacity type instrument. Detecting the current flowing through the ground line, extracting the frequency spectrum based on the sampling data at a certain time during the positive or negative voltage rising process of the primary side input voltage waveform of the transformer for the capacitive instrument among the current signals, Obtain the envelope data of the frequency spectrum as reference envelope data, detect the current flowing in the ground wire of the transformer for the capacitive instrument at the time of measurement, extract the frequency spectrum of the current signal, and envelope the frequency spectrum. Data is obtained as measurement envelope data, and the internal partial discharge of the transformer for the capacitive instrument is obtained by comparing the reference envelope data and the measurement envelope data. And detecting the presence or absence.

The internal partial discharge detection method for a transformer for a capacitance type instrument according to claim 8 is the method for detecting a partial discharge in a transformer for a capacitance type instrument for the purpose of comparison, in which a partial discharge is generated inside the transformer for a capacitance type instrument. The current flowing through the ground line is detected, the frequency spectrum of the current signal is extracted, the fluctuation component of the frequency spectrum due to artificial external noise such as broadcast waves and communication waves is corrected from the frequency spectrum, and the corrected frequency spectrum The envelope data of is obtained as the reference envelope data, the current flowing through the ground wire of the transformer for the capacitive instrument is detected at the time of measurement, the frequency spectrum of the current signal is extracted, and the broadcast wave or communication wave is extracted from the frequency spectrum. The fluctuation component of the frequency spectrum due to artificial external noise such as is corrected, and the envelope data of the corrected frequency spectrum is measured. Obtained as data, and detecting the presence or absence of internal partial discharge of the capacitive voltage transformer and the reference envelope data by comparing with the measured envelope data.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows the configuration of a transformer for a capacitance type instrument to which an internal partial discharge detecting device for a transformer for a capacitance type instrument according to an embodiment of the present invention is applied. In FIG. 1, reference numeral 1 is a transformer for a capacitive instrument, C1 is its high-voltage side capacitor, and C2 is its low-voltage side capacitor.

L is a resonance reactor, G is a secondary short circuit protection gap, and Tr is a transformer. By connecting the terminal V of the transformer for a capacitance type instrument thus configured to ground and applying a voltage to the terminal U, a secondary output voltage is generated between the terminals u and v. In FIG. 1, 3 is a clamp CT for detecting a current flowing through the ground wire 2, 4 is a coaxial cable, 5
Is a terminating resistor. In this way, the current flowing through the grounding wire 2 of the transformer for a capacitive instrument is detected as the voltage signal Vs.

Next, FIG. 2 is a block diagram showing the configuration of an analyzer for inputting the signal Vs shown in FIG. 1 and detecting the internal partial discharge of the transformer for a capacitive instrument. C in FIG.
The PU 20 executes the program previously written in the ROM 21. The RAM 22 temporarily stores the sampling data, frequency spectrum, envelope data thereof, etc. obtained when the program is executed. The amplifier circuit 10 amplifies the voltage signal Vs with a constant bandwidth required to extract the pulse signal due to the internal partial discharge. The sample hold circuit 11 samples and holds the signal. A
The D converter 12 converts the signal into digital data. The CPU 20 gives a timing signal to the sample hold circuit 11 and the AD converter 12 via the I / O port 13 to read the converted digital data. The CRT 14 has a frequency spectrum, its envelope,
The correlation coefficient and the judgment result are displayed. The interface 15 includes a display memory, and outputs a display signal according to the contents to the CRT 14. The CPU 20 displays by writing the data to be displayed in the display memory in the interface 15. The keyboard 16 is used to input measurement start / end instructions, measurement condition settings, and switching between the reference envelope generation mode and the measurement mode. CP
The U20 reads the key operation content via the interface 17. The printer 18 prints out the frequency spectrum, its envelope, the correlation coefficient and the determination result. CP
The U20 controls the printing via the interface 19. The DSP 23 is a digital signal processor, and is used for processing such as FFT (Fast Fourier Transform) performed when obtaining a spectrum on the frequency axis from sampling data on the time axis.

FIG. 3 shows an example of waveforms of the applied voltage and the current flowing through the ground line with respect to the transformer for a capacitive meter shown in FIG.
In FIG. 3, V _PD is the waveform of the voltage applied to the transformer for the capacitive instrument, Ie (0) is the waveform of the current flowing through the ground line when no internal partial discharge has occurred, and Ie (1) is the internal partial discharge. It is a waveform of a current flowing through the ground line in a state where the current is present. Thus, the current Ie flowing through the ground line has a 90 ° phase advance from the voltage waveform due to the capacitance of the voltage dividing capacitor. Usually, partial discharge due to insulation deterioration of one capacitor element of the high-voltage side capacitor occurs in the process (charging process) in which the voltage rises from the zero cross to the peak of the positive or negative half cycle of the applied voltage. If this is represented by the timing of the current signal flowing through the ground line, the partial discharge pulse signal appears at time t2 from t1 to t1 + t2 after the zero cross point of the current Ie. Here, t1 is a time of 1/4 cycle or more of the power supply frequency, and t2 is a time of 1/4 cycle or less of the power supply frequency.
In the embodiment, the internal partial discharge is analyzed based on the sampling data of the t2 period.

FIG. 4 shows an example of the frequency spectrum of the current signal flowing through the ground wire of the transformer for a capacitive meter and its envelope during the period t2 shown in FIG. In FIG. 4, f
1 and f2 are components of the broadcast wave band and the communication wave band.
In this embodiment, in order to avoid the influence of the fluctuation of the frequency spectrum due to the artificial external noise such as the broadcast wave and the communication wave, the spectrum component of the known frequency band is corrected. FIG. 5 is a diagram showing an example thereof. In FIG. 5, the frequencies fa to fb are, for example, the band of the broadcast wave shown as f1 in FIG. 4, and in this case, the frequency spectrum data of the frequencies fa to fb is replaced with the intensity at the frequency fa. That is, the hatched portion in the figure is removed to correct the frequency spectrum.

FIG. 6 shows the envelope data of the frequency spectrum thus obtained. For reference, the reference envelope data in FIG. 6 is the data of the envelope obtained by intentionally causing partial discharge inside the transformer for the capacitance type instrument, and the measurement envelope is the envelope obtained in the actual measurement. The data. Since the center frequency of the envelope changes depending on the impedance of the power system and the capacity of the transformer for capacitive type instruments, when determining the cross-correlation coefficient of these two, one envelope data is fixed and the other envelope curve is fixed. The correlation coefficient is obtained while shifting the frequency axis of the data within a certain range. In this example, when the center frequency of the reference envelope data is fo and the center frequency of the measurement envelope data is fo ′, the frequency difference fs between the two center frequencies is measured within a predetermined range within a predetermined value. The cross-correlation coefficient is obtained while sequentially shifting the envelope data on the frequency axis, and the maximum value thereof is used as the correlation coefficient between the reference envelope and the measurement envelope.

Next, the procedure of the series of processes described above is shown in FIGS. 7 to 9 as a flowchart.

FIG. 7 is a flow chart showing the procedure for generating the reference envelope data. First, one capacitor element constituting the high voltage side capacitor of the transformer for a capacitive instrument is set so as to cause partial discharge, This is set as a normal operation state (n1). In that state, the output signal Vs of the current transformer shown in FIGS. 1 and 2 is sampled for a certain period of time (n2). After that, the zero-cross point of the current signal flowing through the ground wire of the transformer for a capacitive instrument is detected from the sampling data, and the sampling data for a certain period t2 shown in FIG. 3 is extracted with this point as a reference (n3 → n).
4). After that, FFT processing is performed based on the extracted constant number of sampling data for a certain period to obtain a frequency spectrum in a certain frequency range (n5). Further, the power spectrum is obtained from the real number component and the imaginary number component of the frequency spectrum to obtain the frequency spectrum as shown in FIG. 4 (n6). After that, the fluctuation component of the artificial external noise frequency spectrum such as the broadcast wave band is corrected, and the envelope of the corrected frequency spectrum is extracted to obtain the reference envelope data (n7 → n8). After that, the reference envelope data is displayed or printed out as needed (n
9).

FIG. 8 is a flow chart showing the processing procedure of envelope extraction at step n8 in FIG. First, the logarithm of the power spectrum is calculated (n11), and FF is again used.
The cepstrum is obtained by performing T (fast Fourier transform) processing (n12).

After that, the component of the high kefrenshi part of the cepstrum is set to 0 and a predetermined low kefrenshi part is extracted (lifter is performed) (n13). Then, the cepstrum after the lifting is subjected to IFFT (Fast Fourier Inverse Transform) processing to obtain spectrum envelope data (n1
4).

FIG. 9 is a flow chart showing a processing procedure at the time of normal measurement. First, step n shown in FIG.
2 to n8, sampling of the signal Vs, extraction of sampling data for a fixed period, FFT, power spectrum conversion, broadcast wave band correction processing and envelope extraction are performed to obtain measurement envelope data (n21 to n27). ).
Subsequently, the spectrum and envelope data are displayed or printed out as necessary (n28). After that, the center frequency of the measurement envelope data is shifted to a predetermined lower limit (n29), and the initial value 0 is substituted as the maximum correlation coefficient (n30). Then, a cross-correlation coefficient between the reference envelope data and the measured envelope data is calculated (n31).

If the obtained correlation coefficient is larger than the value obtained as the maximum correlation coefficient, that value is stored as the maximum correlation coefficient (n32 → n33). Subsequently, until the center frequency of the measurement envelope data reaches a predetermined upper limit, the frequency axis of the measurement envelope data is shifted by + Δf, and the cross-correlation coefficient with the reference envelope is obtained in that state (n34 → n
35 → n31). This process is sequentially repeated to extract the maximum value of the correlation coefficient obtained by shifting the measurement envelope data in the constant frequency range. Then, it is determined whether or not the obtained maximum correlation coefficient exceeds a predetermined value (0.9 in this example) (n36), and the level (intensity) of the measured envelope data is the level of the reference envelope data. It is determined whether or not it exceeds (n37). If both conditions are satisfied, it is considered that internal partial discharge has occurred, and the notification is given (n3
8). If either one of the above conditions is not satisfied, no notification to that effect is made.

[0029]

According to the internal partial discharge detection device for a transformer for a capacity type instrument according to claim 1 of the present invention or the internal partial discharge detection method for a transformer for a capacity type instrument according to claim 6, the present invention can be performed in an operating state. The state of the internal partial discharge can be reliably detected based on the current signal flowing through the ground wire of a certain transformer for a capacitance type instrument.

According to the internal partial discharge detection device for a transformer for a capacitive instrument according to claim 2 or the internal partial discharge detection method for a transformer for a capacitive instrument according to claim 7, a pulse signal due to an internal partial discharge is included. Since the frequency spectrum is extracted based on the signal only in the time range, it is not strongly affected by external noise that is asynchronous with the power supply frequency, and the S / N ratio is increased.
The detection accuracy of the internal partial discharge is improved.

According to the internal partial discharge detection device for a transformer for a capacitance type instrument according to claim 3 or the method for detecting an internal partial discharge for a transformer for a capacitance type instrument according to claim 8, an artificial wave such as a broadcast wave or a communication wave is generated. Since it is not affected by artificial external noise, the uncertainty due to fluctuations in these artificial external noises is improved.

According to the internal partial discharge detection device for a transformer for a capacitance type instrument according to a fourth aspect, when the correlation coefficient between the reference envelope data and the measured envelope data is larger than a predetermined value, the internal internal discharge is automatically performed. Since the notification that the partial discharge has occurred is given, the detection of the internal partial discharge can be automated without collating the reference envelope data with the measurement envelope and reading the correlation coefficient.

According to the internal partial discharge detecting device for the transformer for a capacitive instrument of the fifth aspect, the level of the measurement envelope data is larger than a predetermined value, and the reference envelope data and the measurement envelope data are combined. When the correlation coefficient is larger than a predetermined value, the notification indicating that the internal partial discharge has occurred is automatically performed.Therefore, the level of the measurement envelope data is read and the reference envelope data and the measurement envelope are The detection of the internal partial discharge can be automated without performing the matching and reading the correlation coefficient.

[Brief description of drawings]

FIG. 1 is a diagram showing a configuration of a transformer for a capacitive meter applied in an embodiment.

FIG. 2 is a block diagram showing a configuration of an analyzer according to the embodiment.

FIG. 3 is a diagram showing an example of a primary input voltage waveform of a transformer for a capacitive instrument and a waveform of a current flowing through its ground line.

FIG. 4 is a diagram showing an example of a frequency spectrum of the current waveform shown in FIG. 3 and its envelope.

FIG. 5 is a diagram showing a method of correcting a variation component of a frequency spectrum due to a broadcast wave or the like.

FIG. 6 is a diagram showing a relationship in obtaining reference envelope data, measurement envelope data, and a cross-correlation coefficient thereof.

FIG. 7 is a flowchart showing a procedure for generating reference envelope data.

FIG. 8 is a flowchart showing a processing procedure of step n8 in FIG.

FIG. 9 is a flowchart showing a processing procedure at the time of measurement.

FIG. 10 is a diagram showing an example of a conventional partial discharge measurement circuit.

[Explanation of symbols]

 1-Capacitance meter transformer 2-Grounding wire 3-Clamp CT (current transformer) 4-Coaxial cable 5-Terminal resistance C1-High-voltage side capacitor C2-Low-voltage side capacitor Tr-Transformer L-Resonance reactor G-2 Secondary short circuit protection gap

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Takanori Tsunoda, 47 Umezu Takaune-cho, Ukyo-ku, Kyoto City, Kyoto Prefecture Nissin Electric Co., Ltd. Within the corporation

Claims (8)

[Claims] 1. A current transformer for detecting a current flowing through a ground wire of a transformer for a capacitive instrument, a frequency spectrum extracting means for extracting a frequency spectrum of an output signal of the current transformer, and a frequency spectrum extracting means for the frequency spectrum extracting means. Envelope data generating means for obtaining envelope data of the extracted frequency spectrum, and for comparison, an envelope curve obtained by the envelope data generating means in the state where partial discharge is generated inside the transformer for capacitive type instrument. Reference envelope data storage means for storing data as reference envelope data, and measurement envelope data temporary storage means for temporarily storing the envelope data obtained by the envelope data generation means during measurement as measurement envelope data, and Internal part of a transformer for a capacitive instrument, comprising correlation coefficient calculating means for calculating a correlation coefficient between the reference envelope data and the measured envelope data. Minute discharge detection device. 2. The frequency spectrum extracting means extracts a frequency spectrum of an output signal of the current transformer at a fixed time during a positive or negative voltage rising process of the primary side input voltage waveform of the transformer for a capacitive instrument. The internal partial discharge detection device for a transformer for a capacitive meter according to claim 1. 3. The frequency spectrum correction means for correcting the fluctuation component of the frequency spectrum due to artificial external noise such as broadcast waves and communication waves from the frequency spectrum extracted by the frequency spectrum extraction means. An internal partial discharge detection device for the transformer for the capacity type instrument described. 4. A detection condition determination that determines whether or not the correlation coefficient obtained by the correlation coefficient calculation means is larger than a predetermined value as a detection condition for the presence or absence of internal partial discharge of the transformer for a capacitive instrument. Means and an informing means for informing that the internal partial discharge has occurred in the transformer for the capacitive instrument when the detecting condition determining means determines that the detecting condition is satisfied. An internal partial discharge detection device for a transformer for a capacitive meter according to claim 1, 2 or 3. 5. The transformer for the capacitance type instrument determines whether the level of the measurement envelope data is larger than a predetermined value and the correlation coefficient calculated by the correlation coefficient calculating means is larger than a predetermined value. Condition determining means for determining whether or not the internal partial discharge of the vessel has occurred, and when the detecting condition determining means determines that the detection condition is satisfied, an internal partial discharge has occurred in the transformer for capacitive instrument. 4. An internal partial discharge detection device for a transformer for a capacitance type instrument according to claim 1, 2 or 3, further comprising an informing means for informing that the fact is indicated. 6. For comparison, the current flowing through the ground wire of the transformer for a capacitive instrument is detected while partial discharge is generated inside the transformer for a capacitive instrument, and the frequency spectrum of the current signal is extracted. Then, obtain the envelope data of the frequency spectrum as the reference envelope data, detect the current flowing in the ground wire of the transformer for the capacitive instrument at the time of measurement, extract the frequency spectrum of the current signal, and extract the frequency spectrum of the frequency spectrum. Obtaining envelope data as measurement envelope data, and comparing the reference envelope data and the measurement envelope data to detect the presence or absence of internal partial discharge of the capacitance instrument transformer, the inside of the capacitance instrument transformer. Partial discharge detection method. 7. For comparison, a current flowing through the ground wire of the capacitance meter transformer is detected with partial discharge generated inside the capacitance meter transformer, and the capacitance type of the current signal is detected. The frequency spectrum is extracted based on the sampling data at a certain time during the positive or negative voltage rise process of the primary side input voltage waveform of the instrument transformer, and the envelope data of the frequency spectrum is obtained as the reference envelope data. The current flowing through the ground wire of the transformer for the capacitive instrument is detected, the frequency spectrum of the current signal is extracted, the envelope data of the frequency spectrum is obtained as the measurement envelope data, and the reference envelope data and the measurement are performed. Method of detecting internal partial discharge of transformer for capacitive instrument by detecting presence or absence of internal partial discharge of transformer for capacitive instrument by comparing with envelope data 8. For comparison, the current flowing through the ground wire of the transformer for a capacitive instrument is detected while partial discharge is generated inside the transformer for a capacitive instrument, and the frequency spectrum of the current signal is extracted. Then, the fluctuation component of the frequency spectrum due to artificial external noise such as broadcast wave or communication wave is corrected from the frequency spectrum, and the envelope data of the corrected frequency spectrum is obtained as the reference envelope data. The current flowing in the ground wire of the instrument transformer is detected, the frequency spectrum of the current signal is extracted, and the fluctuation component of the frequency spectrum due to artificial external noise such as broadcast waves and communication waves is corrected from the frequency spectrum, and the The envelope data of the corrected frequency spectrum is obtained as the measurement envelope data, and the reference envelope data and the measurement envelope data are obtained. Internal partial discharge detection method of displacement instrument transformer for detecting the presence or absence of an internal partial discharge of the capacitive voltage transformer by comparison with.