JPH0221205B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a deterioration detection device for a gear press arrester using a zinc oxide element, and in particular, when the gear press arrester is connected to a high voltage AC power transmission line,
The present invention relates to a gear press arrester deterioration detection device suitable for detecting such deterioration. Conventionally, this type of gear press arrester is used by inserting a large number of sintered bodies (zinc oxide elements) whose main component is zinc oxide connected in series depending on the voltage of the power transmission line between the ground of the power transmission line. . FIG. 1 shows an equivalent circuit of the above zinc oxide element, in which a capacitor C and a resistor R are connected in parallel. Note that the capacitance is due to the high dielectric constant of the zinc oxide element itself. Therefore, the current flowing through the zinc oxide element is the sum of the current I _C flowing through the capacitor C and the current I _R flowing through the resistor R. When the zinc oxide element deteriorates, I _C does not change, but I _R
is increasing. Therefore, by detecting an increase in _IR , it is possible to conversely detect deterioration of the zinc oxide element. However, when the zinc oxide element is normal, _IR is less than a fraction of the current Ic, so it has been difficult to observe _IR for use in determining deterioration. Therefore,
Conventionally, for the purpose of determining the deterioration of zinc oxide elements, attempts have been made to develop deterioration detection devices that use a high-pass filter that blocks frequencies below the fundamental frequency to remove I _C , which consists only of the fundamental frequency, and observe I _R. However, this device had the disadvantage that the deterioration detection device malfunctioned because it measured high-frequency _IC caused by switching impulse voltage and lightning impulse voltage that entered the power transmission line without blocking it in any way. Also,
As stated in Special Publication No. 41-12710,
It is possible to extract only the harmonic components of the current flowing through the zinc oxide element and use this value to determine whether or not the zinc oxide element has deteriorated, but even if only the harmonic components are extracted, the switching impulse voltage and lightning impulse voltage will be affected. There is a risk that the deterioration detection device may malfunction due to the disturbance harmonic current caused by this. An object of the present invention is to provide a gear that can detect the presence or absence of deterioration of a gear press arrester by extracting only the harmonic components of the current flowing through the resistance of a zinc oxide element, excluding disturbance harmonic components. An object of the present invention is to provide a press arrester deterioration detection device. In order to achieve the above object, the present invention includes current detection means that outputs a detection signal in response to a current flowing through a zinc oxide element constituting a gear press arrester, and a current detection means that captures the detection signal of the current detection means and detects the detection signal. A filter means for passing only a harmonic signal having a frequency three times the power frequency of a power source that supplies power to the gear press arrester among the detection signals, and a level of the output signal of the filter means is set to a set value for abnormality determination. This gear press arrester deterioration detection device has a notification means for notifying whether or not the limit has been exceeded. Next, an outline of the present invention will be explained. Since the zinc oxide element is a nonlinear resistor, I _R increases nonlinearly as the voltage increases. Because of this nonlinearity, I _R consists of currents at the fundamental frequency and its harmonic components. On the other hand, the current I _C flowing through the capacitance of the zinc oxide element consists only of fundamental frequency components because the dielectric constant of the zinc oxide element is constant regardless of voltage. Therefore, by blocking the fundamental frequency component of the current flowing through the zinc oxide element, it is possible to extract the harmonics flowing only through I _R without being affected by I _C. By detecting the increase and decrease of this harmonic, it becomes possible to reliably detect the deterioration of the zinc oxide element. Since the zinc oxide element is a non-linear resistor, the current flowing through the gear press arrester depends on the dimensions and charging rate.

[Resistance total current]

= I ₁ sinωt + I ₃ sin (3ωt + φ ₃ ) + I ₅ sin (5ωt + φ ₅ )
+
I ₇ sin (ωt + φ ₇ ) +... Here, ω: commercial frequency, I ₁ , I ₃ ... fundamental wave, third harmonic... peak value of each resistance component current, φ ₃ , φ ₅ ...
Phase difference between 3rd harmonic and 5th harmonic. The fundamental frequency component is the largest, but if this is blocked by a filter, the third harmonic current C is the next largest, and out of the total current of 10 ^-1 mA flowing through the zinc oxide element, it is 10 ^-2 mA. It's the size it occupies.
This is a value that can be measured practically. Embodiments of the present invention will be described below with reference to the drawings. FIG. 3 is an explanatory diagram showing a first embodiment of the gear press arrester deterioration detection device according to the present invention. A gear press arrester 12 composed of a large number of zinc oxide elements is inserted between a power transmission line 14 and the ground. Grounding wire 1 of gear press arrester 12
6 penetrates through the center of a detection coil 18 whose core is a ring-shaped highly magnetic material and is grounded. A current flowing through the gear press arrester 12 is correspondingly induced in the detection coil 18 . The output terminal of the detection coil 18 as current detection means is connected to a bandpass filter 20 that passes only the third harmonic of the power frequency of the power supply that supplies power to the gear press arrester 12. The abnormality determination circuit 24 receives the third harmonic component of _IR , detects an increase in the third harmonic component, and determines whether the zinc oxide has deteriorated, that is, whether the gear press arrester 12 is normal or abnormal. Abnormality determination circuit 24
A display device 26 is connected to display the presence or absence of the above-mentioned abnormality. That is, the abnormality determination circuit 24
The display device 26 constitutes a notification means. A gear press arrester deterioration detection device 28 is constituted by the above 16 to 26. FIG. 4 is a detailed diagram showing the specific circuit of FIG. 3. The current I _C +I _R (see Fig. 1) of the gear press arrester 12 flows through the ground wire 18, and the detection coil 1
8, an electromotive force proportional to (I _C +I _R ) is induced. This induced electromotive force includes not only the fundamental frequency but also harmonic components. Of these, only the third harmonic component is extracted by the bandpass filter 20. This third harmonic is amplified by the amplifier 22 configured with the IC 30 at the next stage. The output terminal of IC30 is connected to the input terminal of IC34 via a diode 32, and the cathode side of the diode 32 is grounded via a capacitor 36.
2. A peak value hold circuit 38 is formed by the capacitor 36 and the IC 34. This peak value hold circuit 38 detects the peak value of the third harmonic after being amplified, and the output voltage of the peak value hold circuit 38 is held at a constant value (DC value) proportional to the peak value. . The abnormality determination circuit 24 includes resistors 40 and 42 that divide the DC voltage V _CC , comparators 44 and 46 , and a resistor that connects the input terminal of each comparator 44 and 46 to the divided voltage or the output terminal of the IC 34 . It consists of This abnormality determination circuit 24 compares a predetermined set voltage obtained by resistor-dividing the DC voltage V _CC with a DC value proportional to the peak of the peak hold circuit 38 . This abnormality determination circuit 24 is equipped with two comparators, and the set voltage of the comparator 46 is lower than the set voltage of the comparator 44. Therefore, when the DC value increases, first the comparator 4
The light emitting diode 48 connected to the output terminal of the comparator 44 via a resistor lights up, and as the DC value further increases, the light emitting diode 50 connected to the output terminal of the comparator 44 via a resistor lights up, and the gear press arrester 12 abnormalities can be displayed in stages. The display device 26 is composed of light emitting diodes 48 and 50. Further, since the ammeter 52 is connected to the output terminal of the IC 34, the resistance current of the gear press arrester 12 can be directly read. Therefore, it is possible to determine whether or not the gear press arrester 12 has deteriorated by directly reading whether the indicated value of the ammeter 52 exceeds the set value for abnormality determination. That is, the ammeter 52 is configured as a notification means. Note that the scale of the ammeter 52 is calibrated so that the resistance current can be directly read. Figure 5 compares the magnitude of each harmonic component of the resistance current of the gear press arrester of this example, where the horizontal axis represents the order n of the harmonic, and the vertical axis represents the magnitude of the harmonic. (n=1 is the fundamental wave 50 or
60Hz). It can be seen that the third harmonic is larger than the other harmonics after the fundamental wave. Figure 6 shows the magnitude of harmonic components in the power transmission system, where the horizontal axis represents the harmonic order n;
The vertical axis represents the magnitude of the fundamental wave and harmonics. In the 70kV system shown by the broken line, the 11th harmonic component is large, and in the 500kV system shown by the solid line, the 5th harmonic component is large. However, it can be seen that the third harmonic component is small in both cases. In other words, in the power transmission system, the third harmonic component of the transmission signal is suppressed to a smaller value than other harmonic components, so the third harmonic current of the current flowing through the resistance of the zinc oxide element is By extracting only this, it is possible to accurately detect the presence or absence of deterioration of the gear press arrester 12. In addition, the switching surge voltage of the grid has a wavefront length of 100~
500μS, wave tail length 2500μS, so 0.5~2.5KHz
It is a high-frequency voltage whose main component is This high frequency voltage causes a current I _C of the same frequency to flow through the zinc oxide element. Also, the lightning impulse voltage is the wavefront length
Since it is 1 μS and the wave tail length is 40 μS, it is a high frequency voltage with a main component of 250 KHz. This high frequency voltage causes
A current with the same frequency flows as I _C. I _C due to surge voltage and lightning impulse voltage affects I _R and causes malfunction. According to this embodiment, only the third harmonic component (150Hz or 180Hz) in the frequency range lower than the frequency components of the switching surge voltage and lightning impulse voltage is extracted and input to the abnormality determination circuit 24, so that the oxidation It has the effect of allowing the current I _R flowing through the resistance of the zinc element to be observed with high sensitivity, and harmonics in the power transmission system, surge voltage during switching, lightning impulses, etc. have many even-order harmonics, and the third Since there are few odd-numbered harmonics including harmonics, there is an effect of preventing malfunctions caused by these and improving reliability. Since the current flowing to the gear press arrester 12 is detected by the detection coil 18 by induction from the grounding wire 16, the large current during the operation of the gear press arrester 12 is not directly shunted to the deterioration detection device 28. This has the effect of preventing damage to the device. FIG. 7 shows a second embodiment of the gear press arrester deterioration detection device according to the present invention. However, the same components as those in the first embodiment are indicated using the same reference numerals. The output of the detection coil 18 attached to the ground wire 16 of the gear press arrester 12 is input to a bandpass filter 20. The output of this bandpass filter 20 is amplified by an amplifier 22. Everything up to this point is the same as the first embodiment. The output end of the amplifier 22 is connected to a light emitting diode 54, and the light emitting diode 54 performs electrical and optical exchange. The light emitting diode 24 is connected to a light receiving diode 58 via an optical fiber 56. This light-receiving diode 58 performs optical-to-electrical conversion, and the output of the light-receiving diode is input to a computer 60. Light emitting diode 54 depending on the output of amplifier 22
undergoes electrical-to-optical conversion, and the light reaches a light receiving diode 58 through an optical fiber 56. When light-to-electrical conversion is performed by the light-receiving diode 58, the output voltage of the amplifier 22 and the output voltage of the light-receiving diode 58 are in a proportional relationship. The computer 60, which receives the output of the light receiving diode 58, makes a judgment similar to that of the above-mentioned abnormality judgment circuit, and issues or records a warning as necessary. Note that the computer 60 is prone to malfunction due to electrical noise, so
Optical fiber 56 is used to prevent the effects of electrical noise. This embodiment also has the same effects as the first embodiment, but since it is computer-processed, precise and detailed observations and records can be made, and reliability is significantly improved. be. As is clear from the above description, according to the present invention, among the harmonic components of the current flowing through the zinc oxide element, only the third harmonic component in the frequency range lower than the frequency component of the disturbance harmonic voltage is indirectly detected. Since the presence or absence of deterioration of the gear press arrester is detected by extraction, it is possible to reliably detect the presence or absence of deterioration of the gear press arrester without malfunctioning due to disturbance harmonic voltage, improving reliability and It can contribute to speeding up measurement.

[Brief explanation of drawings]

Figure 1 is an equivalent circuit diagram of a zinc oxide element (gear press arrester), Figure 2 is a diagram showing the current strength of the fundamental frequency and harmonics with respect to the total current flowing through the resistance of the zinc oxide element. FIG. 3 is an explanatory block diagram showing the first embodiment of the gear press arrester deterioration detection device according to the present invention, FIG. 4 is a detailed block diagram of FIG. 3, and FIG. 5 shows the intensity ratio of harmonic current. FIG. 6 is a diagram showing the ratio of the strength of harmonic current included in the power transmission system, and FIG. 7 is a detailed diagram showing the second embodiment of the gearless arrester deterioration detection device according to the present invention. It is a block diagram. 12... Gear press arrester, 14... Power transmission line, 16... Grounding wire, 18... Detection coil, 2
0...Band pass filter, 22...Amplifier, 2
4... Abnormality determination circuit, 26... Display device.

Claims (1)

[Scope of Claims] 1. Current detection means for outputting a detection signal in response to the current flowing through the zinc oxide element constituting the gear press arrester; filter means for passing only harmonic signals having a frequency three times the power frequency of the power source that supplies power to the press arrester;
1. A gear press arrester deterioration detecting device, comprising: notifying means for notifying whether the level of the output signal of the filter means exceeds a set value for abnormality determination. 2 In the invention described in claim 1,
A gear press arrester deterioration detection device characterized in that the notification means comprises an ammeter. 3 In the invention described in claim 1,
The notification means includes an abnormality determination circuit that compares the output signal of the filter means with a set value for abnormality determination, and outputs an abnormality signal when the level of the output signal of the filter means exceeds the set value; A gear press arrester deterioration detection device comprising: a display device that displays an abnormality in the gear press arrester using an abnormality signal.