JP3077739B2 - Partial discharge measurement method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a partial discharge measuring method for measuring a partial discharge in a high-voltage device, a power cable or the like, and more particularly to a partial discharge measuring method for measuring an S / N ratio optimum for the measurement. It is about.

[0002]

2. Description of the Related Art For example, there is a partial discharge measurement method as a test for detecting a partial defect such as a void or a void in an insulator of a power cable line. For this type of technology, for example,
JP-A-3-170076 and JP-A-3-1700
No. 77 describes this. The partial discharge measurement methods described above detect a noise pulse on a power cable line, simultaneously inject a calibration pulse into the power cable line and detect it, and determine the frequency dependency of the S / N ratio from the frequency spectra of both. I found a frequency with a high S / N ratio,
The partial discharge is measured at this frequency.

[0003] The biggest problem in the measurement of partial discharge in the field is how to deal with external noise. One of the measures against this external noise is the noise gate method.
The optimum frequency Fop is selected, and external noise that has entered at that frequency is removed by the noise gate. The details will be described below. FIG. 3 is a circuit diagram showing an S / N ratio measurement circuit portion of the partial discharge measurement device for performing the partial discharge measurement.

An insulated connecting portion 2 is provided at a connection position of the test cable line 1, and a plurality of metal foil electrodes 3a for signal detection are attached to both sides of the insulating portion. A signal detection impedance 4 is connected to the metal foil electrode 3a, and a spectrum analyzer (SA) 5 for observing a frequency spectrum is connected to the signal detection impedance (Zd) 4.
Is connected. Further, the spectrum analyzer 5 is connected in parallel with a noise gate circuit (NG) 6 and a processing unit 11 for calculating an S / N ratio and selecting an optimum frequency.

[0005] An antenna 7 for detecting noise is disposed near the test cable line 1, and a spectrum analyzer (SA) 9 is connected to the antenna 7 via a noise detection impedance (Zx) 8. Have been.
A gate control circuit (GC) 10 is connected to the spectrum analyzer 9, and an output signal thereof is applied to the noise gate circuit 6. A calibration pulse oscillator (PG) 12 for injecting a calibration pulse signal into the test cable line 1 is connected to the metal foil electrode 3b.

Next, the operation of the above configuration will be described. First, the state without partial discharge and the calibration pulse oscillator 1
2 is stopped and only noise is detected. This noise detection is performed by the metal foil electrode 3a and the signal detection impedance 4.
, And the frequency spectrum (NI (f)) for the noise is obtained by the spectrum analyzer 5.

Next, the calibration pulse oscillator 12 is operated,
A calibration pulse is injected into the test cable line 1 via the metal foil electrode 3b. The calibration pulse is detected by the metal foil electrode 3 a and the signal detection impedance 4, and the electric signal is input to the spectrum analyzer 5.
The frequency spectrum (SI (f)) of the calibration pulse is obtained.

From the above results, the S / N ratio is determined by the following equation. S / N = SI (f) / NI (f) In this equation, the frequency at which S / N becomes the maximum is the optimum frequency Fop. Even when the partial discharge is measured at the optimum frequency Fop, external noise may be mixed in the signal SI (Fop). In this case, external noise is also guided to the antenna 7. Therefore, if the external noise is analyzed by the spectrum analyzer 9 and the noise gate circuit 6 is controlled via the gate control circuit 10, the signal of SI (Fop) is blocked at the moment when the noise is received by the antenna 7, and the SI
External noise mixed into (Fop) can be removed.

FIG. 4 is a signal level-frequency characteristic diagram showing a conventional spectrum measurement result. Optimum frequency Fop is 26
MHz, a calibration pulse of 10 PC was injected from the calibration pulse oscillator 12, and SI (f) and NI (f) were obtained using the output signal of the spectrum analyzer 5. The S / N ratio was about 18 dBm. . In addition, the number of times of noise penetration equivalent to 10 PCs or more of the signal after passing through the noise gate circuit 6 was 18 times per hour.

As described above, first, the optimum frequency Fop is selected by obtaining the S / N ratio, and sudden external noise that rarely enters at the frequency Fop is detected by the antenna 7,
The noise can be removed (or suppressed) by the noise gate circuit 6 based on this signal. The technique of measuring partial discharge is disclosed in JP-A-53-3682, JP-A-54-66480 and JP-A-56-15586.
No. 5 publication. Japanese Patent Laid-Open No. 5-281285 discloses a technique for removing noise.

[0011]

However, in the above-mentioned prior art, when selecting the optimum frequency Fop, the noise removing effect of the noise gate circuit (or the noise removing circuit) is not reflected, and the noise gate is not reflected. The S / N ratio is calculated from the signal at the previous stage of the circuit, and the optimum frequency Fop is selected based on the S / N ratio.
Even if the noise gate circuit is operated by the op, the noise removal effect of the noise gate circuit is not always constant depending on the frequency, so that it may be difficult to remove the noise.

When considered as a total system, it is desirable that the output signal after passing through the noise gate contains as little noise as possible and that the partial discharge signal can be detected with high sensitivity. Further, if a partial discharge is generated from the sample system, the noise gate is reversely dielectrically applied to the antenna system, so that the noise gate may operate and block the partial discharge signal.

Accordingly, it is an object of the present invention to provide a partial discharge measuring method which enables selection of a frequency which is hardly affected by noise.

[0014]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention is directed to a portion for preventing or suppressing signal passage at the time of detection of external noise by noise gate means or noise suppression means. In the discharge measurement method, an S / N ratio is calculated based on a signal output from any of the means, and an optimum frequency of the partial discharge measurement is determined based on the calculated S / N ratio.

In this case, the noise gate means or the noise suppression means may use a phase gate for blocking the passage of a signal having a predetermined phase of the applied voltage. Further, the object is to provide a partial discharge suspected signal of the long power cable line, a plurality of signal detection units for detecting ambient noise, and a detection signal of the signal detection unit provided along the long power cable line. And a plurality of receiving stations for receiving transmission signals transmitted from these transmission stations, and a noise for preventing passage of the partial discharge suspected signal detected simultaneously using the detected noise. A gate; a phase gate for preventing signal passage in a phase other than a predetermined phase width of the phase voltage; and a signal from one insulated connection and another insulation in front of the normal connection adjacent to the insulated connection. A normal connection discriminating gate that passes these signals only when signals from the connection are detected simultaneously, and blocks the passage of these signals when both signals are not detected simultaneously; In a partial discharge measurement system including a persistence gate for extracting only a signal having the persistence of a signal observed in a signal, an S / N ratio is calculated based on a signal passing through the ordinary connection portion determination gate. This is also achieved by determining the optimum frequency of the partial discharge measurement based on the calculated S / N ratio.

[0016]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows the S / S of the partial discharge measuring device which achieves the present invention.
FIG. 3 is a circuit diagram illustrating an N ratio measurement circuit portion. In FIG. 1, the same reference numerals are used for the same components as those in FIG. 3, and thus, duplicate description will be omitted below.

As shown in FIG. 1, in this embodiment, the connection of the processing unit 11 is not the spectrum analyzer 5 but the output of the noise gate circuit 6. As described above, by connecting the processing unit 11 to the noise gate circuit 6, the S / N ratio can be obtained based on the signal in which the noise removal effect is added. That is, as described above, first, only the noise is detected with the calibration pulse oscillator 12 stopped,
The frequency spectrum (NI (f)) for this noise is obtained by the spectrum analyzer 5. Next, the calibration pulse generator 12 can be operated to inject a calibration pulse into the cable under test 1.

On the other hand, external noise received by the antenna 7 is analyzed by the spectrum analyzer 9, and the noise gate circuit 6 is controlled via the gate control circuit 10. At the moment when noise is received by the antenna 7, SI (Fo
The signal passing of p) can be prevented, and external noise mixed into SI (Fop) can be removed. The injected constituent pulse passes through the noise gate circuit 6 controlled in this way and is input to the processing unit 11. In this way, the processing unit 11
/ N ratio is calculated, and the frequency at which the S / N ratio becomes maximum is set as the optimum frequency Fop.

The tuning frequency of the noise taken in from the antenna 7 may be the same as the frequency detected by the spectrum analyzer 5 or an arbitrary frequency. In short, the external noise in the output signal of the spectrum analyzer 5 Any frequency may be used as long as the frequency can effectively remove. FIG.
Is the signal level indicating the spectrum measurement result according to the present invention.
It is a frequency characteristic figure. FIG. 2 shows the S / N ratio detected based on the signal level after passing through the noise gate. The optimum frequency Fop is 18 MHz, and the S / N ratio is 24d.
B. Also, the number of times of noise penetration at the optimum frequency Fop = 18 MHz was 3 times per hour. As described above, by selecting the S / N ratio for the signal after passing through the noise gate circuit 6, the S / N can be increased and the frequency of intrusion of external noise can be reduced.

Note that a phase gate can be used instead of the noise gate. That is, when noise occurs at a constant phase angle (for example, occurrence of thyristor noise),
A signal that has been manually and automatically captured and removed can be used. Further, the other-phase detection signal can be used as a noise detection source. Further, in the partial discharge measurement system proposed in Japanese Patent Application No. 6-39133, the frequency at which the S / N ratio is highest for a pattern display signal such as a φ-gn pattern of a signal using a neural network is determined. You may make it select. Further, the noise gate input signal is not limited to the same tuning frequency as the detection signal, and may be any frequency as long as the noise removal effect is increased at any frequency.

The partial discharge measuring system disclosed in the above-mentioned Japanese Patent Application No. Hei 6-39133 is provided along a long cable line, suspected partial discharge signal of the long cable line, and surrounding noise. A plurality of signal detection units, a plurality of transmission stations for transmitting the detection signals of the signal detection unit as transmission signals, a plurality of reception stations for receiving transmission signals transmitted from these transmission stations, and a plurality of The signal received by the receiving station is at least one of noise detected at the same time, the phase of the corresponding phase voltage of the long cable line, the signal persistence seen in the suspected partial discharge signal, and the signal level.
Some include a plurality of determination units that output a partial discharge suspected signal by processing based on two parameters.

The discriminating section includes a noise gate for preventing passage of the partial discharge suspected signal detected simultaneously using the detected noise, and a phase gate for preventing signal passage in a phase other than a predetermined phase width of the phase voltage. A discriminating gate for preventing passage of a signal from one insulated connection and a signal from another insulated connection ahead of the normal connection adjacent to the insulated connection when these signals are detected simultaneously; , And a sustaining gate for extracting only a signal having the persistence of the signal seen in the partial discharge suspected signal. This partial discharge measurement system has a feature that the measurement accuracy can be improved by accurately distinguishing a partial discharge suspected signal from noise.

The present invention can be applied to such a system, and by applying the present invention, it becomes possible to perform measurement without the influence of noise while maintaining measurement accuracy. That is, by determining the S / N ratio based on the output signal level of the determination gate, the optimum frequency of the partial discharge from the connection portion can be determined. In this case, it is generally impossible to inject a calibration pulse from the connection portion, and therefore, an optimum frequency in which the influence of signal attenuation due to pulse propagation is taken into account is determined.
When selecting the optimum frequency, the tuning frequency for detection of the insulated connection on both sides is slightly changed to upper and lower frequencies, and the optimum frequency is selected based on the output noise level of the normal connection.

In the above embodiment, the measurement of the partial discharge of the power cable line is taken as an example. However, the present invention is not limited to this, and general high voltage equipment, rotating machines, etc.
The present invention is widely applicable when the measurement of the partial discharge is hindered by the intrusion of external noise.

[0025]

As described above, according to the present invention, there is provided a partial discharge measuring method in which, when external noise is detected, signal passage at the time of detection is stopped or suppressed by a noise gate means or a noise suppression means. Since the S / N ratio is calculated based on the signal output from the means, it is possible to reduce the frequency of intrusion of external noise while increasing the S / N ratio.

A plurality of signal detectors are provided along the long cable line to detect a suspected partial discharge signal of the long cable line and surrounding noise, and transmit a detection signal of the signal detection unit to a transmission signal. A plurality of transmitting stations to transmit as, a plurality of receiving stations to receive the transmission signal transmitted from these transmitting stations, and a noise gate to block the passage of the partial discharge suspected signal detected simultaneously using the detected noise,
A phase gate for preventing a signal from passing in a phase other than a predetermined phase width of a phase voltage, and a signal from one insulated connection and another insulated connection beyond the normal connection adjacent to the insulated connection. A normal connection discriminating gate for passing these signals only when the signals are detected at the same time, and blocking the passage of these signals when the two signals are not detected at the same time;
And a sustaining gate for extracting only a signal having the persistence of the signal suspected of the partial discharge suspected signal. By calculating the ratio, it is possible to perform measurement without affecting the external noise without deteriorating the feature of improving measurement accuracy.

[Brief description of the drawings]

FIG. 1 shows the S / D of a partial discharge measuring device for achieving the method of the present invention.
FIG. 3 is a circuit diagram illustrating an N ratio measurement circuit portion.

FIG. 2 is a signal level-frequency characteristic diagram showing a spectrum measurement result according to the present invention.

FIG. 3 is a circuit diagram showing an S / N ratio measurement circuit of a partial discharge measurement device for performing partial discharge measurement.

FIG. 4 is a signal level showing a result of a conventional spectrum measurement.
It is a frequency characteristic figure.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Test cable line 2 Insulated connection part 5, 9 Spectrum analyzer 6 Noise gate circuit 11 Processing part 12 Calibration pulse oscillator

──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Kan Endo 5-1-1, Hidaka-cho, Hitachi City, Ibaraki Prefecture Power System Research Laboratories, Hitachi, Ltd. (56) References JP-A-3-175377 (JP, A) JP-A-7-279877 (JP, A) JP-A-6-308192 (JP, A) JP-A-6-3311691 (JP, A) JP-A-5-33608 (JP, U) (58) Survey Field (Int.Cl. ⁷ , DB name) G01R 31/08 G01R 31/12

Claims (3)

(57) [Claims] When a partial discharge signal detected from a partial discharge measurement point such as a high voltage device or a power cable line is supplied to a signal processing unit via a noise gate unit or a noise suppression unit, and external noise is detected, In the partial discharge measurement method in which the signal passage at the time of detection is blocked or suppressed by the noise gate unit or the noise suppression unit,
A partial discharge measurement method comprising: calculating an N ratio; and determining an optimum frequency of the partial discharge measurement based on the calculated S / N ratio. 2. The partial discharge measurement method according to claim 1, wherein the noise gate means or the noise suppression means uses a phase gate for blocking passage of a signal having a predetermined phase of an applied voltage. 3. A plurality of signal detectors provided along the long power cable line to detect a partial discharge suspected signal of the long power cable line and surrounding noise, and a detection signal of the signal detection unit. A plurality of transmitting stations for transmitting as transmitting signals, a plurality of receiving stations for receiving the transmitting signals transmitted from these transmitting stations, and a noise gate for preventing passage of the partial discharge suspected signal detected simultaneously using the detected noise A phase gate for preventing a signal from passing in a phase other than a predetermined phase width of a phase voltage; A normal connection part discriminating gate that passes these signals only when signals from the parts are detected simultaneously, and blocks the passage of these signals when the two signals are not detected simultaneously; And a persistence gate for extracting only a signal having the persistence of the signal shown in FIG.
A partial discharge measuring method, comprising: calculating a ratio; and determining an optimum frequency of the partial discharge measurement based on the calculated S / N ratio.