JPH112652A - Instrument for measuring leakage current of arrester - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an instrument for measuring leakage current of arrester which can surely and easily detect all leakage currents of an arrester and a capacitive current for cancellation and can accurately measure a resistancecomponent current by taking a higher harmonic component into consideration. SOLUTION: In an instrument for measuring leakage current of arrester, an electric field sensor 15 provided near or on the frame 13 of an arrester detects a system voltage and Fourier transforming sections 16 and 17 find the higher harmonic component and phase at each order by respectively performing Fourier transformation on the detected waveforms of a leakage current and a voltage. Then waveform approximating sections 18 and 19 respectively find the approximate waveforms of both detected waveforms and a differential arithmetic section 20 finds an approximate waveform for cancellation by differentiating the approximate waveforms. Thereafter, a phase adjusting section 21 matches the phases of both approximate waveforms to each other and a level adjusting section 22 matches the levels of the fundamental wave components of both approximate waveforms to each other. Finally, a differential arithmetic section 23 finds a resistance-component current by subtracting the approximate waveform for cancellation from the approximate waveform of the leakage current.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lightning arrester leakage current measuring device using a non-linear resistor as a lightning arrester, and more particularly to a device for measuring resistance leakage current from a lightning arrester leakage current.

[0002]

2. Description of the Related Art This type of lightning arrester has a structure in which a number of non-linear resistors or the like containing zinc oxide as a main component are laminated in a number corresponding to the rated voltage of the system, and is connected to a power system to generate power from a lightning surge or the like. Protect the system.

[0003] As a means for monitoring and maintaining the lightning arrester,
A leakage current measuring device is provided. In this type of arrester,
Deterioration of the lightning arrester appears as a decrease in its non-linearity, and as a result, increases the leakage current of the lightning arrester,
The presence / absence and degree of deterioration of the lightning arrester are detected by measuring leakage current, and the life is further predicted.

The leakage current of an arrester using a non-linear resistor as a lightning arrester is mostly a capacitance current at a normal ground voltage, and the resistance current is considerably smaller than that. However, if the temperature of the lightning arrester rises for some reason, the resistance current will increase, and this increase in the resistance current will appear as an increase in the amount of heat generation. To cause dielectric breakdown.

[0005] Therefore, as a method of monitoring and maintaining and managing the lightning arrester, it is desirable to be able to detect the resistance component current from the leakage current of the lightning arrester.

The equivalent circuit of the arrester is a parallel circuit of a resistor and a capacitor as shown in FIG.
Can be expressed by the combination of the capacitance component current I _C and the resistance component current I _R. From this, the resistance current I _R can be obtained by subtracting the capacitance current I _C from the leakage current I.

As a method for subtracting the capacitance current I _C from the leakage current I, a cancel wave (capacitive component) obtained by differentiating a voltage signal (terminal voltage of the lightning arrester) obtained by the PD (PT) is detected, and the cancel wave is detected. There is a method of extracting the resistance current I _R by obtaining the difference between the wave and the leakage current I.

FIG. 3 shows an example of a leakage current measuring device according to this method. In FIG. 1, a lightning arrester 2 and a voltage detecting voltage divider (PD or PT) 3 are provided between a bus 1 to which a system voltage is applied and a ground.

The total leakage current of the surge arrester 2 is determined by the current transformer (CT).
4 and an amplifier 5 that converts and amplifies the detection current from the current transformer into a voltage signal. The detection voltage of the voltage divider 3 is amplified by the amplifier 6, and this signal is differentiated by the differentiating circuit 7 to obtain a voltage signal of a capacitive component whose phase is advanced by 90 degrees. The level adjusting circuit 8 adjusts the detected voltage peak value (capacitive component) from the differentiating circuit 7 with respect to the detected voltage peak value from the amplifier 5.

The differential amplifier 9 is a lightning arrester 2 provided to the amplifier 5.
Obtain a voltage signal of the resistance component current I _R from the difference calculation between the total leakage current voltage signal and the level adjusting circuit voltage signal equivalent to a capacity of current I _C of the arrester 2 obtained in 8 I of. This resistance current I
_R is displayed on the display 10 and further transmitted to a monitoring device or the like.

The amplifiers 5 and 6 have a harmonic elimination filter to eliminate harmonic components such as lightning surge and noise.

[0012]

The conventional leakage current measuring apparatus has the following disadvantages in measuring the total leakage current of the arrester and measuring the capacitive current for cancellation.

(1) The PD at the substation is a bus 3
In many cases, it is installed in one phase of the power transmission line, and is not necessarily installed near the surge arrester. For this reason,
A voltage signal for obtaining the canceling current must be input to the main body of the leakage current measuring device by extending the cable from the PD secondary terminal box.

(2) When connecting the secondary terminal of the PD, it is necessary to work carefully so as not to cause a malfunction of the relay or an electric shock accident due to a connection error or the like.

(3) In the case of an insulator multi-stage lightning arrester having a high rated voltage, a slight phase difference occurs between the potential of the high-voltage part and the potential of the low-voltage part of the lightning arrester due to the floating capacitance between the ground. Further, when the zinc oxide element is degraded (partially) due to lightning or the like, a large amount of current flows through the resistance, thereby increasing the phase difference (the voltage sharing of the element changes).

On the other hand, as for the voltage waveform, the line voltage (voltage applied to the lightning arrester) measured by the PD is a sine wave (including harmonics), but the voltage waveform at a location where deterioration is large is a distorted waveform. For this reason, when the PD voltage waveform is a cancel wave (capacitive component), an error occurs in the current value of the resistance.

As the number of zinc oxide elements increases (as the rated voltage increases), the voltage sharing becomes non-uniform little by little due to the stray capacitance between the ground and the element. The values are different. For this reason, the total leakage current measured on the lightning arrestor ground side is actually a leakage current flowing to the element near the low voltage part.

(4) The measuring device is subjected to a harmonic filter in order to suppress the influence of noise on both the current and the voltage. Therefore, even if the voltage contains a harmonic, the leakage current waveform and the voltage waveform become sine waves. The waveform becomes close, and an accurate waveform cannot be measured.

When no harmonic filter is provided, if the voltage waveform contains noise or a component having a high order of harmonics, the differential waveform of the voltage waveform used for cancellation is a waveform in which fine vibrations are superimposed. Therefore, it is difficult to measure the resistance component current.

It is an object of the present invention to provide a leakage current measuring device which can surely and easily detect the total leakage current of a surge arrester and the capacitive current for canceling, and can accurately measure a resistance component current in consideration of harmonic components. To provide.

[0021]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention eliminates the need for detection using a PD or PT by detecting a canceling voltage signal by utilizing a stray capacitance in a space around an arrester. In addition, the detection of the leakage current and the capacitive current also includes a harmonic component so as to obtain an accurate resistance component current, and is characterized by the following configuration.

(First Invention) The total leakage current of a lightning arrester having a non-linear resistor as a lightning arrester and the capacitive component contained in the leakage current are detected, and the resistance is reduced by subtracting the capacitive component from the leakage current. In the lightning arrester leakage current measuring device that determines the neutral component, the system voltage to which the surge arrester is connected is detected by an electric field sensor near the low-voltage part of the surge arrester by electrostatic induction based on the stray capacitance of the space, and the detected voltage is differentiated. And determining the capacitive component.

(Second Invention) The total leakage current of a lightning arrester having a non-linear resistor as a lightning arrester and the capacitive component contained in the leakage current are detected, and the resistance is reduced by subtracting the capacitive component from the leakage current. A lightning arrester leakage current measuring device for determining a neutral component, wherein a leakage current detection waveform of the lightning arrester and a detection waveform of a system voltage to which the lightning arrester is connected are Fourier-transformed to calculate a harmonic component and a phase of each order. A waveform approximation means for respectively obtaining an approximate waveform of the two detected waveforms from the calculation; a differentiation means for differentiating an approximate waveform obtained from the detection waveform of the system voltage to obtain an approximate waveform for cancellation; and A phase adjusting means for adjusting the phase of the approximated waveform and the approximated waveform for cancellation; and the level of the fundamental component of the approximated waveform of the leakage current and the approximated waveform for cancellation. And level adjusting means for adjusting the Le, characterized in that a difference computing means for obtaining a resistance component current by subtracting the approximate waveform for canceling the approximate waveform of the leakage current that adjusts the phase and level.

[0024]

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

An arrester provided between the bus 11 to which the system voltage is applied and the ground has an arrester main body 12 supported by a gantry 13. In this support structure, the detection of the total leakage current of the surge arrester main body 12 obtains the detection current from the current transformer 14 as a voltage signal as in the conventional case.

The detection of the capacitive current contained in the total current of the surge arrester is obtained by an electrostatic induction method in which a voltage is measured using a floating capacitance in space, instead of the conventional voltage detection of PD or PT. This method, a portable electric field sensor 15 provided in the provided or frame 13 in the vicinity of the lightning arrester, and the stray capacitance C ₁ between the bus 11 at this position, the stray capacitance between the ground C ₂
By the following equation which is determined by the ratio of, obtaining a voltage signal strength V _S of the electric field is proportional to the system voltage V.

[0027]

V _S = C ₁ * V / (C ₁ + C ₂ ) The electric field sensor 15 is provided inside a cylindrical metal container to prevent induced voltage from other phases and to provide directionality in detection. (Container is grounded). By giving directionality to this electric field detection, it is possible to measure the potential of the bus-side terminal of the surge arrester main body 12 (or the intermediate metal part in the case of a multi-stage lightning arrester).

The configuration described above is a configuration for detecting a leakage current and a canceling voltage. If this configuration is applied to the detection unit of the conventional device, the capacitive current I _C is subtracted from the leakage current I of the surge arrester. In order to obtain the canceling voltage signal for measuring the resistance component current I _R , the detection error due to the other phase is eliminated, and the cable is not laid from the PD terminal required by the conventional device to the measuring device position with the cable. Can be obtained at the lightning arrestor location. In addition, there is no connection error to the PD secondary side terminal.

A current transformer 14 for detecting the total leakage current of the arrester and an electric field sensor 15 for detecting the canceling voltage
Detect the current flowing through the lightning arrester of the surge arrester main body 12 and the applied voltage at the same low voltage side portion. As a result, it is possible to eliminate a detection error of a resistance component current due to a phase difference of a potential between a high voltage portion and a low voltage portion and a difference in a leakage current value caused by deterioration of a lightning arrester having lightning arresters stacked in multiple stages or elements.

Returning to FIG. 1, the calculation elements 16 to 23 calculate the resistance current I _R from the voltage signal of the total leakage current detected by the current transformer 14 and the canceling voltage signal detected by the electric field sensor 15. in a configuration for obtaining a precise resistor-current I _R even if it contains harmonic components (including noise) in the system voltage.

The Fourier transform section 16 performs a Fourier transform on the voltage waveform of the total leakage current I detected by the current transformer 14, and calculates the content and phase of each harmonic component contained in this signal. Similarly, the Fourier transform unit 17 includes the electric field sensor 15
(Or a voltage signal from the PD or PT) is subjected to Fourier transform of a canceling voltage waveform, and the content and phase of each harmonic component included in the signal are calculated.

The waveform approximating sections 18 and 19 use the data from the Fourier transform sections 16 and 17 to obtain voltage waveforms approximating the distorted waves including the harmonic components contained in the respective voltage waveforms. The differential operation unit 20 differentiates the voltage waveform approximated by the Fourier transform unit 19 and calculates a voltage waveform for cancellation.

The phase adjuster 21 adjusts the phase of the approximate waveform of the leakage current from the waveform approximater 18 and the approximate waveform of the canceling voltage from the differential calculator 20. This phase adjustment is performed on the fundamental wave component. The level adjustment unit 22
The levels (peak values) of both approximated waveforms whose phases have been adjusted are adjusted.

The difference calculator 23 calculates the difference between the two approximate waveforms passed through the phase adjuster 21 and the level adjuster 22.
That is, the resistance component current I _R is obtained by subtracting the canceling waveform obtained from the approximate waveform of the voltage differential waveform from the approximate waveform of the total leakage current.

The calculation elements 16-23 described so far will arrangement for determining the detection signal and the resistive component of the current I _R to give an approximate waveform of the fundamental wave from the detection signal of the cancel voltage of total leakage current of the surge arrester. Thus, even when both detection signals include a harmonic component, the resistance current can be accurately obtained.

That is, in the conventional apparatus, since harmonics and noise are removed by a harmonic filter, even when a leakage current includes a harmonic, a comparison is made by a sine wave, and the leakage current including the harmonic component and the capacitance are compared. The current cannot be detected, and the resistance component current from the leakage current and the capacitive current actually flowing in the lightning arrester cannot be obtained. On the other hand, in the present embodiment, the resistance component current can be accurately obtained by detecting the leakage current and the capacitive current including the harmonic component and determining the resistance component current.

The operation elements 16 to 2 in the embodiment are described.
3 is partially or entirely realized by an analog circuit configuration or a digital operation process using a computer.

[0038]

As described above, according to the present invention, since the canceling voltage signal is detected by utilizing the stray capacitance in the space around the lightning arrester, the following effects are obtained.

(1) A canceling voltage signal is transmitted to a PD or PT
It is not necessary to extend the cable from the terminal and take it out, and it can be obtained near the surge arrester.

(2) Since there is no need to connect to the system voltage (PD terminal), the operation is simple and safe.

(3) Since the leakage current and the canceling voltage of the lightning arrester can be detected in the vicinity of the low-voltage portion of the lightning arrester, it is possible to accurately cancel the current corresponding to the capacity from the leakage current even in the high-voltage lightning arrester in which elements are stacked in multiple stages. it can.

Further, according to the present invention, since the detection of the leakage current and the capacitive current includes the harmonic component, even if the system voltage includes the harmonic component or the noise, the resistance component current can be accurately obtained. Can be.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a lightning arrester leakage current measuring device according to an embodiment of the present invention.

FIG. 2 is an equivalent circuit diagram for explaining a leakage current of an arrester.

FIG. 3 is a configuration diagram of a conventional lightning arrester leakage current measuring device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1, 11 ... System bus 12 ... Lightning arrestor main body 13 ... Stand 15 ... Electric field sensor 16, 17 ... Fourier transform part 18, 19 ... Waveform approximation part 20 ... Differential calculation part 21 ... Phase adjustment part 22 ... Level adjustment part 23 ... Difference calculation Department

 ──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor Atsushi Sawada 2-1-117 Osaki, Shinagawa-ku, Tokyo Inside the Meidensha Corporation (72) Inventor Toyohisa Hagiwara 2-1-1, Osaki, Shinagawa-ku, Tokyo Stock Company Inside Shameidensha

Claims (2)

[Claims] 1. A lightning arrester having a non-linear resistor as a lightning arrester detects a total leakage current and a capacitive component included in the leakage current, and obtains a resistance component by subtracting the capacitive component from the leakage current. In the lightning arrester leakage current measuring device, a system voltage to which the lightning arrester is connected is detected by an electric field sensor provided in the vicinity of a low-voltage part of the lightning arrester by an electrostatic induction method based on a stray capacitance of a space, and the detected voltage is differentiated to obtain the capacitance. A lightning arrester leakage current measuring device characterized in that a component is obtained. 2. A lightning arrester having a non-linear resistor as a lightning arrester detects a total leakage current and a capacitive component contained in the leakage current, and obtains a resistance component by subtracting the capacitive component from the leakage current. In the lightning arrester leakage current measuring device, a Fourier transform means for Fourier transforming each of the leakage current detection waveform of the lightning arrester and the detection waveform of the system voltage to which the lightning arrester is connected to calculate a harmonic component and a phase of each order; and Waveform approximating means for respectively obtaining approximate waveforms of both the detected waveforms; differentiating means for obtaining an approximate waveform for cancellation by differentiating the approximate waveform obtained from the detected waveform of the system voltage; Phase adjusting means for adjusting the phase of the approximate waveform for use, and matching the level of the fundamental wave component between the approximate waveform of the leakage current and the approximate waveform for cancellation. And level adjusting means, the leakage current measuring device arrester, characterized in that a difference computing means for obtaining a resistance component current by subtracting the approximate waveform for canceling the approximate waveform of the leakage current that adjusts the phase and level.