JPS6148669B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a surge arrester using a sintered body containing zinc oxide as a main component or a surge arrester using a gap, in order to detect the deterioration of the surge arrester during energization, based on the resistance of the surge arrester. The present invention relates to a leakage current detection device configured to detect leakage current.

First, a conventional example of determining the deterioration state of a lightning arrester using a sintered body containing zinc oxide as a main component (hereinafter referred to as a zinc oxide element) will be described.

A normal zinc oxide element has a considerable capacitance due to its own dielectric constant, and the current flowing through a normal zinc oxide element is mostly the charging current I _C due to the capacitance mentioned above. Therefore, the leakage current I _R due to the resistance can be ignored. Leakage current I _R
When the zinc oxide element is normal, it is about several μA, but as it deteriorates, this leakage current I _R flows from several tens to hundreds of μA, and the deterioration progresses over time, eventually leading to destruction. On the other hand, the charging current I _C is a constant current, usually several hundred μA to several mA, regardless of the presence or absence of deterioration. Therefore, at the initial stage of deterioration, the leakage current I _R is orders of magnitude smaller than the charging current I _C , making it difficult to observe the deterioration determination. The lightning arrester using the element was removed from the overhead wire, a DC voltage was applied to it, and the leakage current _IR due to the resistance was observed to determine deterioration. Therefore, it is necessary to temporarily disconnect from the actual system, and the system cannot be used during the work, which also has the disadvantage of requiring a high-voltage DC power source.

This invention was made to eliminate the drawbacks of the conventional devices described above, and detects the leakage current of the resistance flowing through the zinc oxide element while applying a commercial frequency voltage (voltage of a power transmission line) to the zinc oxide element. In order to do this, the signals from the current detection section that detects the composite current of the charging current flowing through the zinc oxide element and the leakage current and the voltage detection section that detects the voltage applied to the zinc oxide element are processed in a circuit, and phase detection is performed. The deterioration of the zinc oxide element is detected by detecting only the leakage current due to the resistance without being affected by the distortion of the voltage applied to the zinc oxide element. Part 1 below
An embodiment of the present invention will be described with reference to FIGS.

FIG. 1 is a block diagram of the circuit of the leakage current detection device, in which 1 is a power transmission line, 2 is a lightning arrester using a zinc oxide element, 3 is a detection resistor inserted in series with the grounding wire of the lightning arrester 2, and 4 is a A low-pass filter for removing unnecessary high frequency components; 5 is a waveform shaping circuit and a zero-cross comparator that converts the sine wave into a rectangular wave; 6
is a phase detection circuit, 7 is a half-wave rectifier filter circuit, 8 is a multiplier for multiplying the output of the half-wave rectifier filter circuit 7 and the output of the low-pass filter 4, and 9 is the output of the multiplier 8. 10 is a half-wave rectifying and filtering circuit, 11 is a winding type voltage transformer (hereinafter referred to as PT) provided on the power transmission line 1, and 12 is the above-mentioned meter.
Secondary output line of PT11, 13 is the secondary output line 1
2 is an electrode for detecting the secondary output of PT11 by electrostatic induction in a non-contact manner, and 14 is a capacitor for dividing the voltage between the electrode 13 and the capacitance of the secondary output line 12 of PT11. . 15 is a buffer amplifier with high impedance input, 16 is a low-pass filter for removing unnecessary high frequency components, 1
7 sets the phase of the output of the low-pass filter 16 to 90
18 is an amplifier for amplifying the signal attenuated by the differentiating circuit 17;
9 is a waveform shaping circuit, which is a zero-cross comparator that converts a sine wave into a rectangular wave.

2A to 2E are waveform diagrams of main parts for explaining the operation of FIG. 1. In these figures,
20 is the voltage waveform of the power transmission line 1, 21 is the output waveform of the amplifier 18, and 22 is the waveform shaping circuit 1.
The output waveform 9 is the output waveform of the low-pass filter 4, which is a composite waveform of the waveform 24 of the charging current I _C due to the capacitance of the lightning arrester 2 and the waveform 25 of the leakage current I _R due to the resistance component. 26 is a waveform obtained by converting the output waveform 23 of the low-pass filter 4 into a rectangular wave by the waveform shaping circuit 5; 27 is the output waveform of the phase detection circuit 6; and 28 is the output waveform of the half-wave rectifying and filtering circuit 7. Note that FIGS. 2a to 2e are drawn with reference to the topology.

Next, the operation of the embodiment shown in FIG. 1 will be explained with reference to FIG. When the zinc oxide element constituting the lightning arrester 2 begins to deteriorate, a leakage current I _R (waveform in Fig. 2c) due to the resistance flows against the charging current I _C (waveform 24 in Fig. 2c) flowing due to capacitance. 25) can no longer be ignored, and the phase shifts as shown in the output waveform 23 of the low-pass filter 4 in FIG. 2c. Therefore, a current detection unit that detects the current flowing through the lightning arrester 2, that is, a detection resistor 3 connected in series to the ground wire of the lightning arrester 2, detects it as a voltage waveform, and unnecessary high frequency components are removed by a low-pass filter 4. The waveform shaping circuit 5 shapes the waveform into a rectangular wave having a constant amplitude as shown in the waveform 26 in FIG. 2c. On the other hand, the voltage of power transmission line 1,
That is, the voltage waveform 20 shown in FIG. 2a is detected by the voltage detection section. For this purpose, the electrode 1 is connected to the secondary output line 12 of the PT 11 provided on the power transmission line 1 (for example, it is always provided in substations, etc.) without contacting the secondary output line 12 of the PT 11.
3 close to each other, the voltage is divided by the capacitance between the secondary output line 12 and the electrode 13, and the capacitor 14, and the voltage is detected. The buffer amplifier 15 consists of an amplifier having a sufficiently high input impedance relative to the impedance of the capacitor 14, so that the phase does not change. Unnecessary high frequency components are removed from the output of the buffer amplifier 15 by a low-pass filter 16, and the leakage current due to the resistance of the lightning arrester 2 can be ignored, that is, the voltage corresponds only to the charging current flowing due to the capacitance. In order to obtain a waveform (output waveform 21 in FIG. 2b), the differential circuit 17 advances the phase of the output waveform of the low-pass filter 16 by 90 degrees. The reason for using the differentiating circuit 17 is that when there is distortion in the voltage of the power transmission line 1, the phase shifts due to the distortion due to the differential characteristics of the lightning arrester 2. This is to make the output have the same differential characteristics as the lightning arrester 2. The output waveform of the differentiating circuit 17 becomes an output waveform 21 shown in FIG. 2b, and is changed by the waveform shaping circuit 19 into a rectangular wave with a constant amplitude as an output waveform 22 shown in FIG. 2b. In the phase detection circuit 6, the output of the waveform shaping circuit 5 is phase detected by the output of the waveform shaping circuit 19, thereby obtaining an output waveform 27 shown in FIG. 2d. This output waveform 27 is filtered for only the positive or negative half wave by the half-wave rectification filter circuit 7, and the output waveform 28 shown in Fig. 2e is output (in this case, the positive half wave is rectified and filtered). ). By doing this, in the current flowing through the lightning arrester 2, the ratio of the charging current I _C flowing due to the capacitance to the leakage current I _R due to the resistance can be extracted as a DC output. Next, in order to find the absolute value of the leakage current _I By multiplying by the multiplier 8 and displaying the output of the multiplier 8 on the meter 9, the leakage current I
Display only the value of _R.

Incidentally, the lightning arrester 2 uses a resistor with excellent non-linear characteristics, for example, a sintered body whose main component is zinc oxide.
When the leakage current I _R due to the resistance starts to deteriorate and the leakage current I It is not a sine wave like the waveform 25 shown, but due to its non-linearity, it is in phase with the voltage applied to the arrester 2, but it starts to flow rapidly near the peak of the voltage, and hardly flows near the zero voltage. The actual situation is that the waveform is as follows. However, the phase of the composite current flowing through the lightning arrester 2 (composition of charging current I _C due to capacitance and leakage current I _R due to resistance) shifts in proportion to the leakage current due to resistance, so there is no explanation of its operation. No problem. The frequency components of the leakage current I _R due to this resistance are the fundamental wave, that is, the commercial frequency component, and the maximum is the 3rd harmonic component, the 5th harmonic component, the 7th harmonic component, etc. The higher the order of odd-numbered harmonic components, the lower the harmonics, and in practice, it is sufficient to consider up to the 9th harmonic, and the low-pass filters 4 and 16 in FIG. 1 are filters that pass up to the 9th harmonic.

In the above embodiment, the detection resistor 3 is inserted in series with the ground wire of the surge arrester 2 as a method of detecting the current flowing through the surge arrester 2, but in other embodiments, the detection resistor 3 is inserted in series with the ground wire of the surge arrester 2. By detecting the current flowing through the lightning arrester 2, the current flowing through the lightning arrester 2 can be detected regardless of the operation of the lightning arrester 2, so that a more reliable leakage current detection device can be constructed. That is, a current probe using a Hall element is inserted into the ground wire of the lightning arrester 2 as a current detection section without contacting it.

A method for detecting the voltage applied to the lightning arrester 2 is to divide the secondary output voltage of the PT11 using resistors.

A method of dividing the secondary output voltage of PT11 using a capacitor.

A method of directly dividing the voltage of power transmission line 1 using a capacitor.

A method in which electrodes are arranged without contact with the power transmission line 1, that is, at a sufficient distance, and the voltage is divided by the capacitance and capacitor between the electrodes and the power transmission line 1.

Although the above embodiment describes a lightning arrester using a resistor with excellent non-linear characteristics, for example, a sintered body mainly composed of zinc oxide, the present invention is not limited to this, and can be applied to a gap-type lightning arrester. has the same effect and can detect deterioration.

In addition to these lightning arresters, only charging current flows due to capacitance at all times, but due to deterioration or other causes, leakage current flows due to resistance.
For example, the present invention can be similarly applied to insulators for supporting high potential parts.

As explained above, the present invention can determine the deterioration state of a surge arrester by detecting the leakage current due to the resistance component during power application. This has the effect of being able to inspect the It also has the advantage of not requiring a high-voltage DC power source during measurement.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a circuit of a leakage current detection device showing an embodiment of the present invention, and FIG. 2 is a waveform diagram of main parts for explaining the operation of FIG. 1. In the figure, 1 is a power transmission line, 2 is a lightning arrester, 3 is a detection resistor, 4 is a low-pass filter, 5 is a waveform shaping circuit, 6 is a phase detection circuit, 7 is a half-wave rectification filter circuit,
8 is a multiplier, 9 is a meter, 10 is a half-wave rectifier filter circuit, 11 is a wound type instrument transformer, 12 is a secondary output line, 13 is an electrode, 14 is a capacitor, 15 is a buffer amplifier, and 16 is a low-pass filter. , 17 is a differentiating circuit, 18 is an amplifier, and 19 is a waveform shaping circuit.

Claims (1)

[Scope of Claims] 1. A lightning arrester using a zinc oxide element or a lightning arrester using a gap, comprising: a current detection unit that detects a current flowing through the lightning arrester when a normal ground voltage of a power transmission line is applied; A voltage detection section detects the voltage that is present in the current detection section, and a differential circuit advances the phase of the signal from the voltage detection section by 90 degrees to detect the phase of the signal from the current detection section. a circuit for detecting a ratio of a leakage current to a charging current flowing due to the capacitance of the lightning arrester; and a multiplication of the ratio of the leakage current due to the resistance to the charging current due to the capacitance by the magnitude of the current flowing through the lightning arrester. A leakage current detection device comprising: a circuit that detects the magnitude of leakage current due to the resistance of the lightning arrester and detects deterioration of the lightning arrester. 2. The leakage current detection device according to claim 1, characterized in that a resistor is inserted in series with the grounding wire of the lightning arrester as the current detection section. 3. The leakage current detection device according to claim 1, wherein a current probe using a Hall element is inserted into the grounding wire of the lightning arrester in a non-contact manner as the current detection section. 4. The leakage current detection device according to claim 1, characterized in that a wound type instrument transformer is used as the voltage detection section. 5. The leakage current detection device according to claim 4, wherein the secondary output voltage of the wound type potential transformer is divided by a resistor. 6. The leakage current detection device according to claim 4, wherein the secondary output voltage of a winding type potential transformer is divided by a capacitor. 7. The winding instrument transformer is connected to the winding instrument transformer by a high impedance amplifier whose input is an electrode and a capacitor that are brought close to the secondary output line without contacting the winding instrument transformer, and a connection point between the electrode and the capacitor. Claim 4, characterized in that a voltage proportional to the voltage applied to the lightning arrester is obtained by capacitance between the secondary output line and the electrode of the instrument transformer and capacitance division by the capacitor. Leakage current detection device. 8. The leakage current detection device according to claim 1, wherein the voltage is divided using a capacitor as the voltage detection section. 9. The leakage light bulb detection device according to claim 1, wherein the voltage detection section detects the leakage light bulb in a non-contact manner by electrostatic induction by directing an electrode to an overhead wire for applying voltage to the lightning arrester.