JPS604943B2 - Lightning arrester - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION {a- Description of the Technical Field The present invention relates to an earth arrester that has an improved method for detecting characteristic deterioration of an earth arrester that employs a zinc oxide nonlinear resistor.

[b} Description of the Prior Art Conventional lightning arresters have adopted SIC type characteristic elements, but because the nonlinearity was insufficient, it was impossible to create an arrester without a series gap.

However, in recent years, a zinc oxide nonlinear resistor (hereinafter referred to as a trademarked TNR) with excellent nonlinearity has been developed, and it has become possible to realize an earth arrester without a series gap.

On the other hand, the role played by TNR becomes extremely important compared to conventional characteristic elements. For example, when the characteristics deteriorate, the constant leakage current increases, leading to a rise in temperature, and the TN
This may lead to thermal runaway of R. Therefore, it is desirable to periodically check the performance of TNR and understand its characteristics.

By the way, as shown in Figure 1, the characteristics of a lightning arrester are normally checked by grounding the arrester, which consists of a series gap G and a characteristic element RI, through a resistor rl, and detecting the voltage drop across this resistor rl. Ta.

However, in the case of a TNR-based arrester, as shown in Figure 2, the electrical equivalent circuit of the TNR during steady state is a parallel connection of capacitance C2 and non-linear resistance R2, so a The method of detecting the voltage drop across the resistor r2 cannot be said to be effective.

That is, if the applied voltage e and the leakage current flowing through the capacitance C2 and the nonlinear resistor R2 are respectively ic2 and IR2, a phase relationship as shown in FIG. 3 is obtained.

However, it is thought that it is the leakage current iR2 of the non-linear resistor R2 that generates Joule heat and accelerates the deterioration of the TNR, but as shown in FIG.
Although the phase of the resistance leakage current iR2 differs by 90o,
The peak value is in the relationship ic2》iR2. Therefore, even if the leakage current of the TNR is detected by the resistor r2 shown in FIG.
It is difficult to know this because it is masked by the capacitance leakage current ic2.

WObject of the Invention The present invention has been made in view of the above-mentioned problems.
DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below with reference to the drawings.

FIG. 4 shows one embodiment of the power arrester according to the present invention.
A zinc oxide nonlinear resistor (TNR) 1 is housed in an airtight state inside an insulator tube 2. The insulator tube 2 is closed by a high-pressure flange 3 and a grounding frame 4. It is electrically insulated and grounded through a parallel circuit of a capacitor 5 and a non-linear resistor 6. Furthermore, between the non-linear resistor 6 and the ground, there is also a wire of this non-linear resistor 6. An ammeter 7 is inserted to detect the leakage current.'e} Function of the Invention As described above, the TNRI can be expressed as a parallel circuit of capacitance and non-linear resistance in terms of an electric circuit.

Therefore, the electrical equivalent circuit of the earth arrester of the embodiment shown in FIG. 4 is as shown in FIG. In Figure 5, C, and R
, are the capacitance and nonlinear resistance of TNRI, and C2
and R2 correspond to the capacitance 5 and nonlinear resistance 6 shown in FIG. 4 described above.

Here, the values of C2 and R2 are within the range from the normal ground voltage to the rated voltage. = C2R2 is determined so that the relationship holds true.

As shown in Figure 6, the nonlinear resistances R and R2 have the same nonlinear coefficient Q (V = KIQ, V: voltage, 1: current, K: constant), but there is a difference between the constants K and K2. There is a relationship of K,》K2. When the values of C2 and R2 are selected in advance to appropriate values in this way, the voltages e, , e2 applied to the nonlinear resistors R, , R2 and their leakage currents iR, , shown in FIG.
iR2 and the advanced phase current ic, ic of capacitance C, , C2
2 becomes approximately as shown in FIG. That is, iR,=i
Since the relationship R2 is obtained, if the leakage current iR2 of the non-traffic line resistor R2 is detected, the leakage current iR of the resistance R of the TNR can be known, and a highly reliable performance check can be performed. be able to.

{f- Other Embodiments The present invention is not limited to the above embodiments, and the following configurations can be adopted.

That is, this is a configuration in which a variable resistor 61 is used in place of the non-linear resistor 6 in FIG. The equivalent circuit in this case can be represented in FIG. In the lightning arrester constructed as shown in FIG. 8, R2 represents the resistance value of the variable resistor. When a commercial frequency voltage is applied to the line terminal A of the earth arrester constructed in this way, currents iR, ic, and iR2, ic2 flow through each element as shown in Figure 8. By appropriately selecting the variable resistor 61, C.・R,=C2
- It is possible to set it as R2.

A specific method for this is, for example, by observing the voltage waveforms at line terminal A and intermediate terminal B, and determining the value of the resistance value R2 of the variable resistor so that there is no phase difference between them. good.

In this way, it is easy to give each element the above-mentioned relationship C, R, =C2.R2. At this time, the resistance leakage current iR of the characteristic element, the current iR2 of the variable resistor, and the snow protector applied voltage e are approximately as shown in FIG.

iR, is the leakage current of the nonlinear resistor, whereas iR
Since 2 is the current of the linear resistor, the above-mentioned relationship CfR,=C2·R2 cannot be satisfied at all instantaneous values of the applied voltage e. Therefore, as shown in FIG. 9, although the current waveforms iR3 and iR2 cannot be made the same, their peak values are completely the same. That is, i
Since the relationship R, (peak value) = IR2 (peak value) can be easily obtained, by detecting the leakage current iR2 of the variable resistor R2, the leakage current iR, corresponding to the resistance of the TNR resistor R, can be found. This allows for highly reliable performance checks. Still another embodiment of the present invention will be described with reference to FIG.

In this embodiment, a variable capacitor 51 is connected in series with the TNR.
This configuration has a parallel circuit of a linear resistor 62 connected to the ground. In this figure, C and R are the capacitance and non-linear resistance of the TNR, and C2 and R2 correspond to the variable capacitor 51 and the linear resistor 62.
In this configuration, when a commercial frequency voltage is applied to the line terminal A of the lightning arrester, each element has iR, ,
Currents ic2, iR2, and ic2 flow. At this time, by appropriately selecting the value C2 of the variable capacitor 51, it is possible to set R,=C2R2, as in the previous embodiment.U At this time, the resistance leakage current iR of the characteristic element,
The current iR2 of the linear resistor 62 and the voltage e applied to the arrester are approximately the same as those shown in FIG. 9 above. That is, the current waveforms iR,,jR2
cannot be made the same, but the respective peak values will be the same. Therefore, the relationship iR, (peak value) = iR2 (peak value) can be easily obtained, so if the leakage current iR2 of the linear resistor is detected, the leakage current iR, can be known. g' Overall effect As described above, according to the present invention, the resistance leakage current of the TNR can be detected easily and accurately at all times, so that a power surge arrester can be provided which is extremely advantageous in terms of maintenance.

[Brief explanation of drawings]

Figures 1 and 2 are equivalent circuit diagrams showing the conventional deterioration detection method, Figure 3 is a diagram explaining current waveforms, and Figures 4 and 5 are block diagrams of the lightning arrester according to the present invention and its electrical FIG. 6 and FIG. 7 are diagrams showing operating characteristics, FIG. 8 is an equivalent circuit diagram of another embodiment of the present invention, and FIG. 9 is a diagram showing operating characteristics of FIG. FIG. 10 is an equivalent circuit diagram of still another embodiment. 1...Zinc oxide-based nonlinear resistor, 2...
・Insulator pipe, 3...High pressure flange, 4...
Grounding frame, 5... Capacitor, 6... Non-linear resistance, 7... Ammeter, 51... Variable capacitor, 61... Variable resistor, 62...・Linear resistor. Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Figure 8 Figure 9 Figure 10

Claims (1)

[Scope of Claims] 1. In a lightning arrester containing a characteristic element formed by stacking zinc oxide-based nonlinear resistors with excellent nonlinearity, a value equal to the product of the capacitance and the resistance value of the characteristic element. A parallel circuit of a capacitor and a resistor is connected between the characteristic element and the ground, and the leakage current of the resistance of the characteristic element is determined by detecting the leakage current of the resistor of the parallel circuit. Lightning arrester. 2. The lightning arrester according to claim 1, wherein the resistor is a non-linear resistor. 3. The lightning arrester according to claim 1, wherein the resistor is a variable resistor. 4. The lightning arrester according to claim 1, wherein the capacitor is a variable capacitor and the resistor is a linear resistor.