JPH0632256B2 - Method of measuring leakage current of lightning arrester - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial application] The present invention relates to the presence or absence of deterioration of the resistor of a lightning arrester constituted by using a non-linear resistor containing zinc oxide as a main component, or the degree of deterioration. The present invention relates to a measuring method for accurately measuring a so-called leakage current that passes through this resistor under a constant operating voltage for determining.

[Conventional technology]

As shown in FIG. 2, the equivalent circuit of a lightning arrester in which the series gap is omitted by using a resistor having a strong non-linearity, which mainly contains zinc oxide, is shown in FIG. It can be considered that the arrester electrostatic capacitance C including the electrostatic capacitance of is connected in parallel. Therefore, the current i _O flowing through the grounding wire of the lightning arrester becomes a current obtained by combining the resistance leakage current i _R flowing through the non-linear resistance R and the capacitance current i _C flowing through the capacitance C.

Of these, since the resistance leakage current i _R is important for determining the presence or absence of deterioration of the resistor or the degree of deterioration, conventionally, the resistance leakage current i _R is separated from the total leakage current i _O and measured. Various methods have been devised. As an example, when a capacitor is connected in parallel with the arrester and the resistance of the arrester is not deteriorated, the capacitance component current i _C of the arrester is much larger than the resistance component leakage current i _R , so the total leakage current i _O Is substantially equal to the capacitance current i _C , the current flowing through the capacitors connected in parallel is the total leakage current.
After adjusting the capacitor capacity to be equal to i _O ,
A secondary circuit that obtains a difference current between the total leakage current and the current flowing through the parallel capacitor is configured to obtain a resistance leakage current based on the phase difference between the two currents. Further, according to this method, even if the resistor is deteriorated, if the degree of deterioration is small, the resistance leakage current can be obtained with a relatively good approximation.

Also, instead of the capacitor according to the above example, connecting a voltage transformer for the lightning arrestor in parallel and connecting a capacitor on the low-voltage side of the voltage transformer, it is also possible to obtain the resistance leakage current in the same manner as in the above example. it can.

Further, as disclosed in JP-A-61-78086, the peak value position of the total leakage current i _O is detected, and the instantaneous current value at a position deviated by 90 ° from this position is measured as a resistance leakage current. There is also a way to do it.

[Problems to be solved by the invention]

Among the conventional measuring methods, in the method of connecting a capacitor or an instrument transformer in parallel with a lightning arrester, the capacitor or instrument transformer connected in parallel becomes expensive because it is a device connected to a high voltage line, and the existing This method is difficult to apply when the equipment does not have a capacitor or a transformer for instrument connected in parallel with the arrester.

Further, the measuring method according to Japanese Patent Laid-Open No. 61-78086 is effective when the resistance component leakage current i _R is sufficiently smaller than the total leakage current i _O , that is, when the deterioration has not progressed, but the resistance component When the leakage current i _R is large, the phase difference between the peak value position of the total leakage current i _{O and} the peak value position of the resistance leakage current i _R is smaller than 90 °, so the resistance leakage current is There is a problem that it cannot be measured at.

An object of the present invention is to provide a measuring method capable of easily and accurately measuring a resistance leakage current by measuring only a total leakage current i _O of a lightning arrester without requiring an expensive capacitor or an instrument transformer. That is.

[Means for solving problems]

In order to achieve the above object, according to the present invention, the total leakage current flowing in the grounding wire of the arrester configured using a non-linear resistor is separated into a fundamental wave and a harmonic wave, and the phase difference between the two is
An appropriately focused zero point position of the separated fundamental wave waveform and a zero point position of the minimum order higher harmonic wave in the harmonics existing after this zero point position, and the inclination direction of the waveform passing through the zero point is Along with determining the electrical angle of the fundamental wave as the minimum phase difference among the multiple phase differences obtained between the zero point position and the opposite zero point position of the fundamental wave waveform,
The resistance leakage current is measured from this phase difference and the separated basic peak value.

[Action]

According to the present invention, due to the non-linear characteristic of the resistor forming the lightning arrester, the waveform of a half cycle of the resistance leakage current has a high peak value in the central portion and is symmetrically and rapidly attenuated toward both skirts. It focuses on having a waveform. The principle of the measuring method according to the present invention will be described below.

As described above, the resistance leakage current i _R has a waveform whose half cycle has a high peak value in the central portion and has a waveform which is symmetrically and rapidly attenuated from this peak value toward both skirts. , In addition to the fundamental wave component, it contains many odd harmonics. The peak value of each order component is R ₁ , R
I _R can be expressed by the following equation, where ₃ , R ₅ , ....

i _R = R ₁ sin ωt + R ₃ sin 3ωt + R ₅ sin 5ωt + ……………… (1) On the other hand, the capacitance component current i _C is 90 ° ahead of i _R , so the peak value is C ₁ . Then, it can be expressed by the following equation.

i _C = C ₁ sin (ωt + 90 °) (2) Since the total leakage current i _O is a combination of i _R and i _C ,
It is expressed by the following equation.

Here, φ is the phase difference expressed in electrical angle between the zero point position of the waveform of the fundamental wave after the synthesis and the zero point position of the resistance leakage current before the synthesis that follows this zero point position. Can be represented.

φtan ^-1 (C ₁ / R ₁ ) (4) In addition, the peak value of the fundamental wave in the front leakage current i _O can be calculated from equation (3). Therefore, solving equations (4) and (5) for C ₁ gives Is obtained. Therefore, the resistance leakage current i _R is calculated from the total leakage current, and the capacitance current C ₁ sin (ωt + 90 °) = C
It is obtained by subtracting ₁ cos ωt. To this end, the measured total leakage current is divided into a fundamental wave component and a harmonic component to obtain the peak value of the fundamental wave component, and the zero point position of this fundamental wave component and the resistance following this zero point position The time difference (phase difference) from the zero point position of the fundamental wave only in the partial leakage current must be obtained from the separated waveform.

By the way, as described above, the waveform of the resistance leakage current is a waveform that has a high peak value in the central portion and is symmetrically and rapidly attenuated toward both skirts. Since the zero point of the fundamental wave component is substantially determined by the third harmonic component that passes through the fundamental wave waveform with an inclination in the opposite direction, the zero point position of the focused fundamental wave component and the separated third harmonic component In the waveform of, the time difference is obtained between a plurality of zero point positions after the zero point position of the fundamental wave, which has a slope in the opposite direction to the inclination direction of the fundamental wave waveform at the zero point position of the focused fundamental wave, If the minimum value of is represented by the scale of the electrical angle of the fundamental wave, the phase angle represented by the above equation (4) can be obtained.

Thus, by separating the total leakage current into the fundamental wave component and the harmonic components, the peak value of the fundamental wave component in the total leakage current and the total leakage current and the resistance component leakage current that cannot be measured directly. It becomes possible to obtain the phase difference between the fundamental wave components in the, and the resistance component can be accurately measured even when the leakage current increases due to the resistance component without using the expensive capacitor and the transformer for instrument as in the past. The leakage current can be obtained.

〔Example〕

FIG. 1 shows an embodiment of a measuring instrument structure which enables the leakage current measurement by the method of the present invention.

The lightning arrester 1 is inserted between the high voltage line HV and the ground E. The total leakage current i _O flowing through the ground wire 2 of the lightning arrester 1 is detected by the current transformer 3 and input to the measuring device 4. If a clamp type current transformer having a split iron core structure is used as the current transformer 3, i _O can be conveniently detected without attaching or detaching the ground wire.

The measuring device 4 divides one cycle of the input total leakage current i _O into minute times and stores the current value at each divided moment, and a sampling means 4a and the stored current value at each moment. To calculate the total leakage current i _O
Separating means 4b for separating a fundamental wave component and a harmonic wave component, which serves as a filter, a peak value of the separated fundamental wave, a zero point following the peak value, and a slope direction of the waveform at the zero point position. And a harmonic wave data detecting means 4d for detecting the zero point position of the third harmonic wave in which the inclination direction of the waveform is opposite to the inclination direction of the fundamental wave in response to the zero point detection signal. And the time difference between the zero point position detected by the fundamental wave data detecting means 4c and the zero point position detected by the harmonic wave data detecting means 4d is obtained, and the minimum time difference among the time differences is selected and the electrical angle scale of the fundamental wave is selected. Phase difference detecting means 4e for expressing and outputting
And the peak value of the fundamental wave detected by the fundamental wave data detecting means 4c and the phase difference output from the phase difference detecting means 4e, the peak value of the capacitive current is obtained, and the peak value is obtained. And a display means 4g for displaying the resistance leakage current waveform obtained by the calculation means 4f or the peak value thereof. Therefore, since the measuring process from the input of the total leakage current to the measuring device 4 to the display of the resistance leakage current is automatically performed, only the measuring device 4 and, for example, the clamp type current transformer 3 are connected. By preparing, the capacitor and the transformer for the instrument are not connected in parallel with the lightning arrester, and therefore the existing equipment, which cannot judge the deterioration of the lightning arrester by the conventional method, must be interrupted for the preparation for measurement. It is possible to measure the resistance component leakage current of the lightning arrester extremely easily and highly accurately.

〔The invention's effect〕

As described above, according to the present invention, the total leakage current flowing in the grounding wire of the arrester configured by using the non-linear resistor is separated into the fundamental wave and the harmonics, and the phase difference between them is An appropriately focused zero point position of the separated fundamental wave waveform and the zero point position of the minimum order higher harmonic wave in the higher harmonic wave existing after this zero point position, and the inclination direction of the waveform passing through the zero point is the basic point. The minimum phase difference among the multiple phase differences obtained between the zero point position and the opposite zero point position of the wave waveform is obtained on the scale of the electrical angle of the fundamental wave, and this phase difference and the separated basic Since the resistance leakage current is measured from the peak value of the wave, this leakage current can be accurately measured regardless of the magnitude of the resistance leakage current that is directly related to the deterioration of the arrester. For expensive capacitors and instruments Allowing accurately degradation determination without using the divider. In addition, this measurement method is a method that can automatically advance all measurement steps from the input of the total leakage current to the display of the resistance leakage current by using a microcomputer. For the existing equipment that does not have the resistance leakage current measuring means, only the prepared measuring instrument and the total leakage current flowing through the grounding wire of the arrester are prepared, for example, a clamp type current transformer. In addition, the resistance leakage current can be measured without interrupting the operation for preparation for measurement.

[Brief description of drawings]

FIG. 1 is a functional block diagram showing an embodiment of a measuring device configuration that enables the leakage current measuring method of the present invention, and FIG. 2 is an equivalent circuit diagram of a lightning arrester. 1 ... Lightning arrester, 2 ... Ground wire, 3 ... Current transformer, 4 ... Measuring instrument, 4a ... Sampling means, 4b ... Separation means,
4c ...... fundamental data detecting means, 4d ...... harmonic data detecting means, 4e ...... phase difference detecting means, 4f ...... calculating means, 4g ...... Display unit, i _R ...... resistive leakage current, i _O ... …
Total leakage current.

Claims (2)

[Claims] 1. A total leakage current flowing through a grounding wire of a lightning arrester constructed by using a non-linear resistor is separated into a fundamental wave and a harmonic wave, and a phase difference between the two is appropriately determined based on the waveform of the separated fundamental wave. Exists at the zero point position focused on and after this zero point position,
A plurality of positions determined between the zero point position of the zero-order position of the lowest order harmonic in the harmonic and the inclination direction of the waveform passing through the zero point is opposite to the inclination direction of the zero point position of the fundamental wave waveform. Measured as a minimum phase difference in the phase difference on the scale of the electrical angle of the fundamental wave, and measuring the leakage current of the surge arrester characterized by measuring the resistance component leakage current from this phase difference and the peak value of the separated fundamental wave Method. 2. The leakage current measuring method according to claim 1, wherein all the measuring steps from the separation of the total leakage current flowing through the ground wire into the fundamental wave and the harmonic wave to the resistance leakage current measurement are performed. A method of measuring a leakage current of a lightning arrester, which is characterized by being automatically advanced by using a microcomputer.