JPH08320353A - Leakage current detection device of zinc oxide type lightning arrester - Google Patents

Abstract

PURPOSE: To accurately measure resistance current by providing a computing unit for extracting the leakage current of a fundamental frequency by a filter and for approximating the characteristics between the leakage current and resistance current. CONSTITUTION: Leakage current flowing to a lightning arrester 1 is detected by a current transformer 3 and is inputted to a filter 20. The leakage current becomes only a fundamental wave component after passing through the filter 20. A computing unit 21 approximates the characteristic curves of the resistance current when the lightning arrester 1 is normal and the fundamental frequency component of leakage current. When the fundamental wave component of the leakage current is inputted, an output signal becomes resistance current. The resistance current is inputted to a display 6 to detect resistance current, thus principally and easily detecting resistance current without any detection error due to the high harmonic of an applied voltage.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a leakage current detecting device for detecting a resistance component current of a zinc oxide type arrester.

[0002]

2. Description of the Prior Art FIG.
FIG. 3 is a block diagram showing a conventional leakage current detection device for a lightning arrester disclosed in Japanese Patent Laid-Open No. 0-58, wherein 1 is a lightning arrester composed of a zinc oxide element, 2 is a ground wire of the lightning arrester 1, and 3 is a Rogowski type. Current transformer 4, 4 is a third harmonic filter that passes only the third harmonic of the output of the current transformer 3, 5 is an amplifier, 6 is a display for displaying the resistance current, and 7 is for executing the operation described later. Is a constant input device.

A conventional leakage current detecting device for a zinc oxide type arrester employs a method of detecting a resistance component current from the third harmonic component of the leakage current to be detected.

Next, the operation will be described with reference to FIG. 15 together with the outline of the conventional technique. The conventional leakage current detection device is focused on that a third harmonic is generated in the resistance current when a sinusoidal voltage is applied due to the resistance current-voltage characteristic having nonlinearity. The analysis revealed that the resistance current-voltage characteristic can be approximated by an odd-order function of the voltage, and the resistance current can be calculated from the third harmonic current if the proportional coefficient of each order is known. is there.

That is, when a sinusoidal voltage is applied to the zinc oxide arrester, the resistance leakage current flowing through the ground wire has a distorted waveform shown in FIG. If the resistance leakage current is represented by I _R (t) with time as t, I _R (t) = − I _R (−
t) and becomes a periodic target wave. This resistive component current I _R with a nonlinearity as shown in FIG 16 - can be explained from the voltage V characteristics. That is, when the voltage of V _IN is applied, I _R −
According to the V characteristic, V _IN is converted into a current, which is distorted I _OUT and is output. This is just like the current amplification effect of a transistor. The change of the resistance leakage current I _R with respect to the voltage V is

I _R (V) = − I _R (−V) (1)

Therefore, I _R is expressed by an odd-order function of V and is given by the equation (2).

I _R = A ₁ V + A ₃ V ³ + A ₅ V ⁵ + ... (2)

Equation (2) is approximated by terms up to the fifth order, and V
The sine wave voltage

V = V ₀ sinωt (3)

When expressed by, the equation (2) becomes the equation (4).

I _R = (A ₁ + 3 / 4A ₃ V ₀ ² + 5 / 8A ₅ V ₀ ⁴ ) V ₀ sinωt + (-1 / 4A ₃ V ₀ ² + 11 / 16A ₅ V ₀ ⁴ ) V ₀ sin 3ωt + 1 / 16A ₅ V ₀ ⁵ sin5ωt (4)

The first term on the right side of the equation (4) represents the fundamental wave, and the second and third terms represent the third and fifth harmonics, respectively. Now, the third harmonic is a measurable quantity, and the measured value is I _R3 sin3ω
If t, then equation (5) is obtained.

(-1 / 4A ₃ V ₀ ² + 11 / 16A ₅ V ₀ ⁴ ) V ₀ = _{IR 3} (5)

Since A ₃ and A ₅ are known, the unknown quantity is
There is only V ₀ , and it can be calculated by the equation (5). By substituting the obtained V ₀ into the equation (4), the magnitudes of the fundamental wave, the fifth harmonic, and the resistance current I _R can be obtained. In particular,
When equation (2) is approximated by terms up to the third order, equations (4) and (5) are simplified to equations (4-1) and (5-1).

[0016] _{I R = (A 1 + 3} / 4A 3 V 0 2) V 0 sinωt -1 / 4A 3 V 0 3 sin3ωt (4-1) -1 / 4A 3 V 0 3 = I R3 (5-1)

Substituting equation (5-1) into equation (4-1),

I _R = [A ₁ × (-4I _R3 / A ₃ ) ^1/3 -3I _R3 ] sinωt + I _R3 sin3ωt (6)

And I _R is calculated from I _R3 much easier. As shown in FIG. 14, a conventional leakage current detecting device for a zinc oxide type lightning arrester has a Rogowski current transformer 3 mounted on a ground wire 2 of a lightning arrester 1 composed of a zinc oxide element, and outputs the same. The 3rd end only passes the 3rd harmonic
It is connected to the harmonic filter 4. The filter 4 extracts only the third harmonic of the resistance current flowing through the connection line 2 and inputs it to the amplifier 5. The amplifier 5 is connected to the calculator 7. Calculator described above by the constant input device 8 to 7 (2) of the proportional constant _{A 1, A 3, A 5} , ···· is input. In the calculator 7, from the input constant and the magnitude of the third harmonic current input from the amplifier 5,
Calculation is performed according to the equations (4) and (5) or (6), and the magnitude of the third harmonic current is converted into the magnitude of the resistance component current. The converted value is displayed on the display 6 and directly read. It should be noted that the proportional constants A ₁ , A ₃ , A ₅ , ... Can be changed and input for each target lightning arrestor each time, and the calculator 7 also has software for that purpose.

[0020]

Since the conventional leakage current detecting circuit for the lightning arrester is constructed as described above, when the voltage applied to the lightning arrester includes the voltage of the third or fifth harmonic component. , resistance of the current I _{Rm ax} measurement results without occurrence of the error is avoided, and also (6) by the formula has a problem such operations include term for obtaining the cube root is complex.

The present invention has been made in order to solve the above problems, and a simple calculation can be performed even when the voltage applied to the arrester includes the voltages of the third and fifth harmonic components. It is an object of the present invention to obtain a leakage current detecting device for a zinc oxide type arrester, which can accurately measure the resistance current I _Rmax just by using it.

[0022]

A zinc oxide surge arrester according to claim 1 of the present invention is a filter for extracting a leakage current of a fundamental frequency component, and a leakage current and a resistance of the fundamental frequency component extracted by the filter. And a calculator that approximates one or more characteristics between the split currents.

According to a second aspect of the present invention, there is provided a zinc oxide lightning arrester according to the first aspect, wherein in the leakage current detecting device for the zinc oxide lightning arrester according to the first aspect, the arithmetic unit operates between the leakage current of the fundamental frequency component and the resistance component current. The approximation of the characteristics is performed by linear approximation.

A zinc oxide surge arrester according to a third aspect of the present invention is the leakage current detecting device for a zinc oxide surge arrester according to the first aspect, which stores a resistance component current value corresponding to the leakage current value of the fundamental frequency wave component. According to the measured value of the leakage current of the fundamental frequency wave component, the arithmetic unit reads the resistance current value from the corresponding storage area and obtains the resistance current.

A zinc oxide surge arrester according to claim 4 of the present invention is the leakage current detecting device for a zinc oxide surge arrester according to claim 1, in which the arithmetic unit is configured to have the fundamental frequency of each of the leakage current and its capacitive component current. The sine value of the phase difference δ between the components (sin
δ) is multiplied by the leakage current value of the fundamental frequency component.

A zinc oxide surge arrester according to a fifth aspect of the present invention is the leakage current detecting device for a zinc oxide arrester according to any one of the first to fourth aspects, in which the temperature around the zinc oxide arrester is measured. The operating unit switches the characteristic between the fundamental frequency component of the leakage current and the resistance component current based on the detected temperature value.

A zinc oxide surge arrester according to a sixth aspect of the present invention is the leakage current detecting device for a zinc oxide surge arrester according to any one of the first to fourth aspects, and detects a deteriorated state of the zinc oxide arrester. A deterioration detector is provided, and the arithmetic unit switches the characteristic between the leakage current and the resistance component current of the fundamental frequency component based on the detected deterioration state.

[0028]

In the zinc oxide type arrester according to claim 1 of the present invention, the filter extracts the leakage current of the fundamental frequency component, and the arithmetic unit between the leakage current of the fundamental frequency component and the resistance component current extracted by the filter. One or more of the above characteristics are approximated.

In the zinc oxide surge arrester according to claim 2 of the present invention, the arithmetic unit performs linear approximation to approximate the characteristic between the leakage current of the fundamental frequency component and the resistance component current.

In the zinc oxide type arrester according to claim 3 of the present invention, the memory device stores the resistance current value corresponding to the leakage current value of the fundamental frequency wave component, and the arithmetic unit stores the fundamental frequency wave component. The resistance current value is read from the corresponding storage area according to the leakage current measurement value to obtain the resistance current.

In a zinc oxide type arrester according to a fourth aspect of the present invention, the arithmetic unit has the sine value (sin δ) of the phase difference δ between the fundamental wave frequency components of the leakage current and its capacitive component current and the basic The leakage current value of the frequency component is multiplied.

In the zinc oxide arrester according to claim 5 of the present invention, the temperature detector measures the temperature around the zinc oxide arrester, and the leakage current is detected based on the temperature value detected by the calculator. Switches the characteristics between the fundamental frequency component and the resistance component current.

In the zinc oxide type arrester according to claim 6 of the present invention, the deterioration detector detects the deterioration state of the zinc oxide type arrester, and the arithmetic unit detects the deterioration state of the fundamental frequency component. Switches the characteristics between leakage current and resistance current.

[0034]

【Example】

Example 1. An embodiment of the present invention will be described below with reference to the drawings. In FIG. 1, reference numeral 20 is a filter that passes only a fundamental frequency (commercial frequency) component of the leakage current, and 21
Shows a computing unit according to the first embodiment of the present invention. The same reference numerals as those in FIG. 14 indicate the same objects as those in FIG. FIG. 2 shows characteristic curves of the basic frequency (commercial frequency) components of the resistance current and the leakage current when the zinc oxide type arrester is normal.

It is known that the leakage current when the zinc oxide type arrester is normal is mostly occupied by the capacity current, and the resistance current is almost negligible. It is known that the electrostatic capacity of a zinc oxide type arrester is hardly changed by voltage, and the capacity current changes its magnitude in proportion to the applied voltage of the arrester.

The capacitive component current I _cn of each order component from the fundamental frequency (commercial frequency) component to the harmonic component is expressed by equation (7).

I _cn = n · ωCV _n (7)

Here, n: harmonic order (n = 1, 2, 3) ω: angular frequency (= 2πf, f is commercial frequency) C: electrostatic arrester capacitance V _n : applied voltage of each component

As is apparent from the equation (7), the capacitive component current I _cn of the harmonic component is affected n times as much as the variation of the applied voltage V _n of the component. On the other hand, the fundamental frequency component is n =
Since it is 1, it is proportional to the applied voltage V _n .

As described above, the leakage current and the current corresponding to its capacitance are substantially equal. From this, it can be seen that if the fundamental wave component of the leakage current is selected, it becomes a signal proportional to the applied voltage. That is, it can be seen that a similar characteristic curve (FIG. 2) can be obtained even if the fundamental frequency component I ₀₁ of the leakage current is replaced instead of the voltage of the resistance current-voltage characteristic. According to the method of the present invention, the resistance component current is obtained from the characteristic curve of the resistance component current I _R- the basic frequency component I ₀₁ of the leakage current. As described above, according to the method of the present invention, in principle, the resistance component current can be easily detected without a detection error due to the harmonic component of the applied voltage.

Next, the operation will be described with reference to FIGS. Note that FIG. 2 corresponds to FIG. 16 described as the conventional technique. The current transformer 3 detects the leakage current flowing through the lightning arrester 1. The leakage current becomes only the fundamental wave component I ₀₁ after passing through the filter 20. The arithmetic unit 21 to which I ₀₁ is input imitates the characteristic curve of I _R -I ₀₁ of FIG. 2, and the output signal thereof becomes the resistance current I _R. The I _R signal is input to the display 6 to detect the resistance current.

Example 2. The second embodiment of the present invention will be described below. FIG. 3 is a circuit diagram showing an arithmetic unit according to the second embodiment. The arithmetic unit 21a shown in FIG. 3 is a lightning arrester by partially modifying the circuit of FIG. 10-7 of P174 of "Design of OP Amplifier Circuit" (Takuo Okamura, 10th edition, November 1, 1977). The I _R -I ₀₁ characteristic of is linearly approximated. In the figure, 100 to 104, 107, 109 and 110 are resistors, and their resistance values are shown in the figure. Reference numerals 105 and 106 are diodes, and 108 and 111 are operational amplifiers. V _s is a signal obtained by converting the fundamental frequency component I ₀₁ of the total leakage current into an appropriate voltage level.

The operation of the operational amplifier 108 in the preceding stage will be described. The anode side of the diode 105 and the cathode side of the diode 106 are connected to the input terminal of the operational amplifier and are in an imaginary short-circuit to ground. Therefore, the voltage applied to the diodes 105 and 106 becomes zero when V _s = R ₁ / R ₂ V _B and V _s = + R ₁ / R ₂ V _B. Since the forward voltage of the diode is a negligible value, when V _s ≦ −R ₁ / R ₂ V _B , the diode 105 conducts and the resistor 102 is connected in parallel with the resistor 102.
The amplification degree A _FN at this time can be expressed by the following equation.

A _FN = −Rf / (1 / (1 / R _s + 1 / R ₁ ) = − Rf · (1 / R _s + 1 / Rf)

Here, R ₁ / R ₂ V _B > V _s > −R ₂ / R ₂
At V _B , diodes 105 and 106 are non-conducting. The amplification degree A _FN at this time can be expressed by the following equation.

A _FN = -R _f / R _s

When V _s ≧ R ₁ / R ₂ V _B , the diode 10
Since 6 is conductive, the resistor 103 is in parallel with the resistor 102. The amplification degree A _FN at this time can be expressed by the following equation.

A _FN = -R _f (1 / R _s + 1 / R _f )

A graph of these relationships is shown in FIG. The output voltage V ₀ of the amplifier 108 is the amplifier 111,
By passing through the inverting amplifier circuit composed of the resistors 109 and 110, the output voltage V ₀ ′ having the amplification degree −R ₄ / R ₃ is obtained. The relationship between the V ₀ 'and V _s signals is obtained by linearly approximating the characteristic curve of I _R -I ₀₁ shown by the broken line in FIG. In addition, it is possible to subdivide the linear approximation section as necessary.

According to the second embodiment, since the circuit can be configured by an analog circuit, there is an effect that the software for calculation and an expensive digital element are not required and the circuit can be configured at low cost.

Example 3. Next, a third embodiment of the present invention will be described. In the second embodiment, the calculation is processed in an analog manner, but in the third embodiment, a case in which the calculation is digitally calculated will be described. FIG. 6 shows a circuit configuration in the arithmetic unit 21b in this case.

In FIG. 6, 200 is an A / D conversion circuit for converting an analog signal into a digital signal, and 201 is an RO.
M, the resistance component current of the zinc oxide type arrester 1 to be detected-
The characteristics of the voltage simulation signal are stored. 202 is a computing unit 2
A central CPU 1b, 203 is a D / A conversion circuit for converting a digital signal into an analog signal, and the output of the D / A conversion circuit 203 is connected to the display 6 shown in FIG.

Next, the operation of the third embodiment will be described.
The signal I ₀₁ of the fundamental frequency component of the leakage current is input to the A / D conversion circuit 200, and the digital output corresponding to the signal is input to the A / D.
Input from the conversion circuit 200 to the CPU 202.

The CPU 202 reads out the resistance current value corresponding to the digital signal value from the ROM 201 and inputs the digital value to the D / A conversion circuit 203. D / A
The conversion circuit 203 converts the digital value into an analog value and sends it to the display 6. By sequentially executing this series of operations, the resistance current is obtained.

Since the digital processing is performed in the third embodiment as described above, setting and data management are facilitated. Also,
There is an effect that there is no calculation error due to temperature drift or the like.

Example 4. In the first to third embodiments, the resistance current is detected in the form including the harmonic component.
When the detection of the resistance current of the fundamental frequency component is required, the circuit as shown in FIG. 7 can be used for the calculator 21c.

First, FIGS. 8 and 9 will be described. Figure 8 shows the electrical equivalent circuit of a zinc oxide type arrester,
A circuit in which a nonlinear resistance and a capacitor are connected in parallel is shown.
When a voltage V is applied to the zinc oxide arrester, a leakage current I ₀ that is a combination of the resistance component current I _R and the capacitance component current I _C flows in the zinc oxide arrester. Figure 9 shows the applied voltage at that time,
It is a vector diagram of the commercial frequency of each electric current.

The operation of FIG. 7 will be described using the above. The peak value of the fundamental frequency component of the leakage current is detected by the peak value detector 3
00 is required. The value is input to the sinδ determination circuit 301. The sinδ determination circuit 301 determines the sinδ value according to the input value. δ corresponds to δ in the vector diagram shown in FIG. 9. The result of (peak value of fundamental wave of total leakage current × sin δ) is output to the output of the multiplication circuit 302. This result corresponds to the peak value of the resistance current of the vector of FIG.

The conversion circuit 303 converts the peak value into a signal form suitable for the connected display unit 6. The fourth embodiment has an effect that it is suitable for the specification of obtaining the fundamental frequency component of the resistance component current.

Example 5. In each of the above-mentioned embodiments, the resistance current and the applied voltage characteristic have been considered to be constant. It is known that the voltage-current characteristics of the zinc oxide element described on page 11 (issued in December 1993) change depending on the ambient temperature of the element as shown in FIG.

In order to accurately measure the resistance current peak even in such a case, as shown in FIG. 10, the temperature detector 4 is provided around the zinc oxide type arrester or at a place corresponding thereto.
00 and the selection circuit 401 for selecting the I _R -I ₀₁ characteristic according to the output signal thereof is provided in the arithmetic unit 21d.

For example, when applied to the analog type characteristic approximation circuit of the second embodiment, the approximation circuit may be provided and the output thereof may be switched by the selection circuit 401 in accordance with the number of temperature points to be switched. If it is applied to the third embodiment, the data may be stored according to the number of temperature points to be switched, and necessary characteristic data may be extracted according to the output signal of the selection circuit 401.
According to the fifth embodiment, there is an effect that the resistance current peak can be accurately detected even when the ambient temperature changes.

Example 6. In addition to the ambient temperature, depending on the deterioration state of the lightning arrester, for example, as the VI characteristics of the zinc oxide element disclosed on page 37 of the document of Example 5, the characteristics change due to the element deterioration as shown in FIG. . In this case as well, in order to accurately measure the resistance current peak, FIG.
Instead of the temperature detector 400 shown in FIG.
0 may be provided, and the selection circuit 401a similar to that of the fifth embodiment may be provided in the arithmetic unit according to the output signal.

As described above, according to the fifth embodiment, there is an effect that the resistance component current can be accurately detected even when there is a deterioration state.

[0065]

The zinc oxide surge arrester according to claim 1 of the present invention has a filter for extracting the leakage current of the fundamental frequency component, and the leakage current and the resistance component current of the fundamental frequency component extracted by the filter. Since it has an arithmetic unit that approximates one or more characteristics, without using a complicated arithmetic expression,
Further, there is an effect that the resistance component current can be detected by a simple calculation without causing a detection error due to the harmonic component.

According to a second aspect of the present invention, in the zinc oxide type arrester of the present invention, in the leakage current detecting device for the zinc oxide type arrester of the first aspect, the arithmetic unit operates between the leakage current of the fundamental frequency component and the resistance component current. Since the approximation of the characteristics is performed by the linear approximation, the calculation software and the expensive digital element are not required, so that the cost can be reduced.

A zinc oxide surge arrester according to a third aspect of the present invention is the leakage current detecting device for a zinc oxide surge arrester according to the first aspect, in which a resistance component current value corresponding to the leakage current value of the fundamental frequency wave component is stored. Since the arithmetic unit is configured to read the resistance current value from the corresponding storage area according to the measurement value of the leakage current of the fundamental frequency wave component and obtain the resistance current, data management and calculation are performed. The effect is excellent in accuracy. Further, there is an effect that a calculation error due to a temperature change does not occur.

The zinc oxide surge arrester according to claim 4 of the present invention is the leakage current detecting device for a zinc oxide surge arrester according to claim 1, in which the arithmetic unit is configured to have the fundamental frequency of each of the leakage current and the current corresponding to its capacitance. The sine value of the phase difference δ between the components (sin
Since δ) is multiplied by the leakage current value of the fundamental frequency component, there is an effect that it is suitable for specifications for obtaining the fundamental frequency component of the resistance component current.

The zinc oxide type arrester according to claim 5 of the present invention is the leakage current detecting device for a zinc oxide type arrester according to any one of claims 1 to 4, wherein the temperature around the zinc oxide type arrester is measured. Since the arithmetic unit is equipped with a temperature detector that switches the characteristics between the fundamental frequency component of the leakage current and the resistance component current based on the detected temperature value, the accuracy is improved even if the ambient temperature changes. The effect is that the resistance current can be detected well.

A zinc oxide arrester according to claim 6 of the present invention is the zinc oxide arrester leakage current detecting device according to any one of claims 1 to 4, wherein the deterioration state of the zinc oxide arrester is detected. Since the arithmetic unit is equipped with a deterioration detector and switches the characteristics between the leakage current and the resistance current of the fundamental frequency component based on the detected deterioration state, the resistance component can be accurately measured even if the element deteriorates. This has the effect of being able to detect a current.

[Brief description of drawings]

FIG. 1 is a circuit diagram of a leakage current detection device for a zinc oxide surge arrester showing a first embodiment.

FIG. 2 is an operation explanatory diagram of the first embodiment.

FIG. 3 is a circuit diagram of an arithmetic unit according to a second embodiment of the present invention.

FIG. 4 is an operation explanatory diagram of FIG. 3;

5 is an operation explanatory diagram of FIG. 3;

FIG. 6 is a circuit diagram of an arithmetic unit according to a third embodiment of the present invention.

FIG. 7 is a circuit diagram of an arithmetic unit according to a fourth embodiment of the present invention.

8 is an explanatory diagram of the operation of FIG. 7.

FIG. 9 is an operation explanatory diagram of FIG. 7;

FIG. 10 is a circuit diagram of a leakage current detecting device for a zinc oxide type arrester showing a fifth embodiment of the present invention.

FIG. 11 is an operation explanatory diagram of FIGS. 10 and 12;

FIG. 12 is a circuit diagram of a leakage current detecting device for a zinc oxide type arrester showing a sixth embodiment of the present invention.

FIG. 13 is an operation explanatory diagram of FIGS. 10 and 12;

FIG. 14 is a circuit diagram of a leakage current detection device for a conventional zinc oxide surge arrester.

15 is an explanatory diagram of the operation of FIG.

16 is an explanatory diagram of the operation of FIG.

[Explanation of symbols]

1 lightning arrester, 2 ground wire, 3 current transformer, 5 amplifier, 6
Display, 20 filter, 21, 21a-e arithmetic unit, 400 temperature detector, 401, 401a selection circuit, 500 deterioration detector.

Claims (6)

[Claims] 1. A leak current detection device for a zinc oxide surge arrester, which detects a leak current of a zinc oxide surge arrester and calculates a resistance current thereof, and a filter for extracting a leak current of a fundamental frequency component, and the above filter. A leakage current detection device for a zinc oxide surge arrester, comprising: a calculator that approximates one or more characteristics between the extracted leakage current of the fundamental frequency component and the resistance current. 2. The leakage current detection device for a zinc oxide surge arrester according to claim 1, wherein the arithmetic unit performs linear approximation to approximate the characteristic between the leakage current of the fundamental frequency component and the resistance component current. Leakage current detector for surge arrester. 3. The leakage current detection device for a zinc oxide surge arrester according to claim 1, further comprising a storage device for storing a resistance current value corresponding to the leakage current value of the fundamental frequency wave component, wherein the computing unit is the A leakage current detector for a zinc oxide surge arrester, which reads the resistance current value from the corresponding storage area according to the measured leakage current of the fundamental frequency wave component and obtains the resistance current. 4. The leakage current detecting device for a zinc oxide surge arrester according to claim 1, wherein the arithmetic unit is a sine value (sin δ) of a phase difference δ between the fundamental current frequency components of the leakage current and its capacitive component current. ) And the leakage current value of the fundamental frequency component are multiplied, the leakage current detecting device of the zinc oxide surge arrester according to claim 1. . 5. The leakage current detecting device for a zinc oxide type arrester according to claim 1, further comprising a temperature detector for measuring a temperature around the zinc oxide type arrester, wherein the computing unit comprises: A leakage current detection device for a zinc oxide surge arrester, which switches the characteristic between the fundamental frequency component of the leakage current and the resistance component current based on the detected temperature value. 6. The leakage current detection device for a zinc oxide surge arrester according to claim 1, further comprising a deterioration detector for detecting a deterioration state of the zinc oxide surge arrester, wherein the arithmetic unit detects A leakage current detection device for a zinc oxide surge arrester that switches the characteristics between the leakage current of the fundamental frequency component and the resistance component current based on the deteriorated state.