JPH0541527Y2 - - Google Patents

Description

[Detailed Description of the Invention] Industrial Application Field The present invention relates to a lightning arrester that is applied in oil to protect power equipment from abnormal voltages such as lightning surges.

BACKGROUND ART In recent years, in the electric power field, the demand for a stable supply of electric power has increased more than ever before, and efforts have been made to improve the reliability of electric power equipment and the quality of electric power.
In particular, with the aim of improving the quality of electricity, zinc oxide-based lightning arresters, which usually do not have a gap, have been put into practical use in order to reliably absorb and suppress harmful abnormal voltages generated by lightning on power transmission and distribution lines. They are installed at various locations in power transmission and distribution equipment. In particular, the practical use of lightning arresters built into power equipment with improved protection performance is rapidly progressing. A varistor element whose main raw material is zinc oxide is built inside these lightning arresters without a gap as a characteristic element, and the characteristics of this varistor element itself become the characteristics of the lightning arrester. From this point of view, it is important to have a lightning arrester housing that can exhibit the surge absorption characteristics of the varistor element as well as the characteristics of the varistor element.

Conventionally, the internal structure of this type of lightning arrester is shown in Figure 2.
The configuration was as shown in Figure 3. Figure 2 is a typical type of built-in power equipment, and shows a cross section of a lightning arrester that is applied in oil in an oil-immersed power distribution transformer, and does not show how it is installed on the transformer.
In Fig. 2, numeral 1 is a cylindrical varistor element having a cylindrical hollow part, which is obtained by sintering zinc oxide as the main raw material and adding additives such as bismuth and praseodymium at high temperature. An insulating layer is provided on both outer sides, and electrodes are formed on both end faces of aluminum metallicon (both not shown). Figure 2 shows a state in which four varistor elements are connected in series. As shown, the required number of such varistor elements are installed in series according to the applicable rating of the lightning arrester. Reference numeral 2 denotes an insulating rod which penetrates the hollow part of the varistor elements 1 connected in series and fixes the varistor elements 1 and the entire lightning arrester, and is usually made of glass-filled epoxy. Reference numeral 3 denotes a charging terminal, which is pressed into contact with the electrode on the end surface of the uppermost stacked varistor element 1, and at the same time, one end thereof is connected to a line of a power distribution line (not shown). 4 is a grounding terminal which is press-contacted to the electrode on the end face of the lowermost varistor element 1, and at the same time, one end thereof is connected to the ground of equipment (not shown), and also serves as a mounting bracket for the entire lightning arrester. The charging terminal 3 and the grounding terminal 4 are both made of a good conductor, such as a copper alloy. Reference numeral 5 denotes a coiled spring provided on the top of the charging terminal 3 to provide the pressure contact force necessary for pressure contact, 6 a stopper at one end of the spring 5, and 7 similarly fixing the stopper 6 and for adjusting the pressure contact force. It is fixed by tightening a nut to a male screw provided at the end of the insulating rod 2. A nut 8 has the same function as the nut 7, and is attached to the lower part of the ground terminal 4. Reference numeral 9 denotes an electrode plate inserted between the ground terminal 4 and the nut 8, and has an oil hole communicating with the hollow part of the varistor element 1.

The arrester shown in FIG. 2 is applied in the insulating oil of the transformer, and the insulating oil flows not only outside the arrester but also into the hollow part of the varistor element 1. FIG. 3 shows a plane cross section of parts A to B shown in FIG. 2, and the gap between the hollow part of the varistor element 1 and the insulating rod 2 becomes an oil passage for insulating oil.

The behavior of the conventional lightning arrester configured as described above when absorbing a surge current will be described below.

First, when a lightning surge voltage is applied across the charging terminal 3 and the grounding terminal 4 of a lightning arrester, a surge current accompanying those voltages flows through the lightning arrester, suppressing the voltage across the lightning arrester. At this time, the surge current passes through the series-connected varistor element 1,
The energy consumed at that time becomes Joule heat,
Once the temperature of the varistor element 1 is raised, then
Heat is radiated from the outer and inner surfaces of the varistor element 1 to the insulating oil.

Problems to be Solved by the Invention However, in such a conventional configuration, there is a gap between the insulating rod and the hollow part of the varistor element. There is a risk that the elements may be misaligned with each other, and this misalignment poses a problem in that the discharge withstand capacity of the lightning arrester is reduced.

The present invention aims to solve these problems, and is designed to prevent the varistor element from shifting during assembly or due to external mechanical force.
It is also intended to maintain the oil permeability of the hollow portion of the varistor element.

Means for Solving the Problems In order to solve the above-mentioned problems, the present invention has a hole in the center between the varistor elements with a diameter slightly smaller than the inner diameter of the hollow part of the varistor element. the varistor element is thicker than the adjacent portion;
It is constructed by inserting an intermediate electrode plate having a thickness step to prevent the varistor element from shifting, and inserting an insulating rod into each hollow part or hole.

Effects Because the present invention has the above-described configuration, a thickness step is provided at the edge of the hole in the intermediate electrode plate, so this step prevents the varistor element from shifting when assembled or when an external mechanical force is applied. Does not occur. In addition, since there is a sufficient difference in diameter between the outer diameter of the insulating rod and the inner diameter of the hole in the intermediate electrode plate,
The oil permeability properties are the same as conventional ones.

Embodiment FIG. 1 shows an embodiment of the lightning arrester of the present invention, and the same figure shows a cross section of the lightning arrester applied in oil of an oil-immersed power distribution transformer. In Figure 1, 1
0 is a varistor element whose main material is zinc oxide, 11
is a charging terminal, 12 is a grounding terminal, 13 is a spring, 14 is a stopper, 15 and 16 are nuts, 17 is an electrode plate, and 18 is an insulating rod, which are the conventional varistor element 1, charging terminal 3, and grounding terminal, respectively. 4, spring 5, stopper 6,
This corresponds to the nuts 7 and 8, the electrode plate 9, and the insulating rod 2. 19 is an intermediate electrode plate according to the present invention;
0 is a thickness step provided at the center 12 of this intermediate electrode plate 19, around the periphery (edge) of a hole whose diameter is slightly smaller than the inner diameter of the hollow part of the varistor element 10, and where the varistor element 10 is thicker than the adjacent part. It's summery. Since a surge current passes through the intermediate electrode plate 19, a copper alloy, aluminum, or the like having excellent conductivity is used. In addition, the intermediate electrode plate 19
are used in the adjacent portions of the varistor element 10, and three pieces are used in FIG.

Next, the operation of the lightning arrester configured as above will be explained. Similar to the conventional example, when a lightning surge voltage is applied across the charging terminal 11 and the grounding terminal 12 of the arrester, the surge current accompanying those voltages flows through the arrester, suppressing the voltage across the arrester. At this time, the surge current flows through the varistor element 1 connected in series.
0, the energy consumed at that time becomes Joule heat, and once the varistor element 10
After that, heat is radiated from the outer and inner surfaces of the varistor element 10 and the intermediate electrode plate 19 to the insulating oil, and cooling is performed by the insulating oil flowing in and out of the hollow part of the varistor element 10. .

By using the intermediate electrode plate 19 having such a shape, it is possible to prevent misalignment of the varistor elements 10 when vertically stacking them, as well as misalignment due to external mechanical force. Since there is a sufficient difference between the inner diameter of the intermediate electrode plate 19 and the diameter of the insulating rod 18, the same oil permeability as in the prior art can be obtained.

In the embodiment of the present invention, the spring 13 has a coil shape, but it may also be a flat spring or a spring washer. In this case, if the electrode plate 17 is also used on the opposite side (upper side), the oil permeability will not be affected. Further, the thickness step 20 does not necessarily have to be continuous and ring-shaped.

Effects of the invention As described above, according to the invention, a hole with a diameter slightly smaller than the inner diameter of the hollow part of the varistor element is provided in the center between the varistor elements, and a step in thickness is provided on the inner periphery of the hole. By inserting the intermediate electrode and passing an insulating rod through the hollow part of the varistor element and the hole in the intermediate electrode plate to form an oil-submerged lightning arrester, it is possible to prevent misalignment when assembling the varistor elements vertically. This has the advantage of being able to prevent positional displacement due to external mechanical forces, and also maintaining oil permeability for cooling the varistor element.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing a lightning arrester according to an embodiment of the present invention, FIG. 2 is a sectional view showing a conventional lightning arrester, and FIG. 3 is a plan sectional view of parts A to B of FIG. 10... Varistor element, 11... Charging terminal, 1
2...Ground terminal, 13...Spring, 14...
Stopper, 15, 16... Nut, 17... Electrode plate, 18... Insulating rod, 19... Intermediate electrode plate, 2
0...Thickness step.

Claims (1)

[Scope of utility model registration request] A hole with a diameter slightly smaller than the inner diameter of the hollow part of the varistor element is formed in the center between the varistor elements, which are made by stacking a plurality of cylindrical varistor elements each having a cylindrical hollow part and electrodes on both end faces. rice cake,
An intermediate electrode plate is inserted into the inner peripheral part of the hole, which is thicker than the part adjacent to the varistor element and has a thickness step to prevent the varistor element from shifting;
A lightning arrester characterized in that an insulating rod is passed through a hollow part and a hole in each of the varistor element and the electrode plate.