JPH01255439A - Arrester - Google Patents

Abstract

PURPOSE:To suppress the temperature rise of a varistor element by securing a cylindrical varistor element and a discharge gap through an insulating rod extending from a power device, leading electric terminals from both ends and intermediate part thereof, and bringing insulation oil in the tank of the device into direct contact with the varistor element. CONSTITUTION:When a surge voltage or a short time overvoltage is generated continuously or for a long period of time, the element temperature of a varistor element 15 is extremely raised by absorbed energy. However, the heat sink from the element 15 is uniformly conducted directly to insulation oil 27 in a tank 22, the specific weight of the oil 27 exposed with high temperature becomes light, and the flow of the stripelike oil 27 is formed along the outside face of the element 15. Thus, the heat sink effect of the element 15 is largely improved to suppress the temperature rise of the element 15 to a low value.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a lightning arrester for use in oil for protecting power equipment from abnormal voltages such as lightning surges.

BACKGROUND OF THE INVENTION 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, in order to improve the quality of electric power, zinc oxide type lightning arresters without series gaps have been put into practical use in order to reliably absorb harmful abnormal voltages generated on power transmission and distribution lines due to lightning, etc. installed in various locations. Also,
From the viewpoint of economically improving the protection characteristics of power equipment, lightning arresters built into power equipment are also being put into practical use. This type of lightning arrester built into power equipment is typically used in transformers submerged in oil, but these arresters are constantly exposed to the high temperature of the insulating oil of the transformer, and the temperature is higher when applied in air. Therefore, sufficient heat dissipation must be considered for surge current absorption and short-term AC overvoltage application.

Therefore, how to dissipate the heat generated from the elements that are the characteristic elements of lightning arresters has become an important issue.

Conventionally, the internal structure of this type of lightning arrester was as shown in FIG. The lightning arrester shown in FIG. 4 is an example of application in transformer oil, and some of the components of the transformer are also shown. In Figure 4, 1 is a cylindrical varistor element obtained by high-temperature sintering using zinc oxide as the main raw material, adding additives such as bismuth and praseodymium, and in the example shown in the figure, 4 elements are connected in series by pressure welding. has been done. 2 is a coiled spring for fixing and pressing the varistor element 1; 3 is the varistor element 1;
It is also an insulating case that houses the spring 2, and usually a hollow insulator is used. 4 is the charging terminal of the lightning arrester, 6
is a metal cap that seals and fixes the entire contents stored in the insulating case 3, and is fixed to the insulating case 3 by caulking.

6 is an oil hole provided on the charging terminal 4 side of the insulating case 3;
7 is a grounding terminal, 8 is a grounding lead wire from the grounding terminal 7, 9
is a transformer tank, to which a ground lead wire 8 is connected, and the tank 9 itself is also grounded. 1o
1 is a charging lead wire connected to the charging terminal 4; 11 is an insulating plate made of an insulator, and is provided with a voltage tap switching terminal of a transformer, etc. 12 is a high voltage lead wire, and an insulating plate 11
It is connected to the charging lead 10 at the top and at the same time to the high voltage winding (not shown) of the transformer. 13 is the iron core of the transformer, 14 is filled with insulating oil up to the part indicated by the broken line A, and the entire lightning arrester is contained in this insulating oil 14.

Regarding the heat dissipation of the conventional lightning arrester configured as above,
The operation will be explained below.

First, when lightning surge voltage, switching surge voltage, or short-time AC overvoltage is applied across the arrester, the surge current associated with those voltages is bypassed by the arrester, and the surge voltage on the line to which the arrester is connected is suppressed. . At this time, the surge current passes through the series-connected varistor elements 1, and the energy consumed at that time becomes Joule heat, which increases the temperature of the varistor element 1, and then mainly the varistor element 1. Insulating case 3 from the side of
Heat is radiated to the insulating oil 14 inside, and further heat is radiated by passing the oil through the insulating case 3 and the oil passage hole e.

Problems to be Solved by the Invention However, in such a conventional configuration, when the above-mentioned surge voltage or short-time AC overvoltage occurs continuously or for a long time, the There was a problem that heat dissipation through oil passage was not sufficient. That is, in the conventional configuration, the flow of the insulating oil, which is a heat transfer medium, is limited to the vicinity of the oil passage hole 6, and the flow of the insulating oil at the side surface of the varistor element 1 is hardly expected.

In addition, the surge voltage rises very steeply (dma/(
(It is large), even if the limiting voltage is kept low by the lightning arrester, the potential gradient within the high-voltage winding of the transformer will be partially severe. Figure 6 shows the situation. 1 in the same figure is a circuit diagram of the high voltage winding.
The opening is the winding start part of the winding, and C is the winding part from which the winding start part is removed.

b in the same figure shows the entire potential gradient when a surge voltage is applied to the high voltage winding. Figure 6bKS-The potential gradient is the same in all parts of the winding for low-frequency voltages, as shown by straight line 2, but for high-frequency voltages, such as surge voltages, the curved line shows the same potential gradient. The potential gradient at the beginning of the winding is more severe than that at the other parts, which poses a problem in that the interlayer insulation of the winding is threatened. Furthermore, since the activation voltage is increased to prevent the lightning arrester from being destroyed even in the event of a short-term AC overvoltage, the limiting voltage is also high.

The present invention aims to solve all of these problems.The present invention aims to improve the heat dissipation characteristics of the varistor element through the flow of insulating oil surrounding the varistor element, improve the thermal stability of the lightning arrester when handling large amounts of energy, and further improve the thermal stability of the lightning arrester during large energy processing. The objective is to provide a lightning arrester that has a uniform potential gradient, maintains interlayer insulation coordination, and has a low limiting voltage.

Means for Solving the Problems In order to solve the above problems, the present invention fixes a cylindrical varistor rider and a discharge gap via an insulating rod extending from a power device, and takes out electrical terminals from both ends and the middle of the rod. These are connected to the ends of the windings of the electrical equipment, the ground, and the tap terminals in the middle of the windings, so that the insulating oil in the tank of the power equipment comes into direct contact with the varistor elements.

Effect of the Invention With the above-described configuration, the insulating oil heated by the heat generated by the varistor element has a light specific gravity, and the insulating oil can uniformly flow upward from the bottom to the top along the outer surface of the varistor element. This greatly improves the heat dissipation effect from the side surfaces of the varistor element. In addition, by connecting a varistor element to the tap terminal in the middle of the winding, it has the effect of making the potential gradient within the winding uniform even against steep surge voltages, and furthermore, a discharge gap is connected in series to the ground terminal side. Therefore, the operation start voltage of the varistor element can be lowered, and therefore the limiting voltage is also lower.

Embodiment FIG. 1 is a sectional view showing a lightning arrester according to an embodiment of the present invention, and is an example of application in transformer oil. In Figure 1, 1
Reference numeral 6 denotes a varistor element mainly made of zinc oxide, which has a hollow cylindrical shape and has a ring-shaped metallicon electrode on each end surface.

Further, in FIG. 1, three varistor elements 16 are connected in series. Reference numeral 16 denotes a discharge gap, which has a hollow part like the varistor element 15, and is provided with a ring-shaped discharge gap part 161L, and the discharge gap part 16& and the outside are two cylinders 16b and 160 made of ceramic or glass.
It is sealed and kept airtight. The discharge gap section 1
62L is filled with an inert gas such as nitrogen. Further, the discharge gap 16 is arranged to be located at the end on the ground side. Reference numeral 17 denotes an insulating rod, one of which is fixed to an L-shaped metal fitting 28 attached to an iron core 26 of a transformer, which will be described later. Since this insulating rod 17 is immersed in insulating oil, a resin or ceramic rod with good oil resistance, or a metal rod coated with an insulating coating is used. 18 is a nut, together with a spring washer and a spring (both not shown).
The varistor element 16 and the discharge gap 16 are fixed by an insulating rod 17 passed through the hollow part of the varistor element 16 and the discharge gap 16. Reference numeral 19 denotes a ground terminal, which is brought out in pressure contact with the electrode of the discharge gap 16 located at one end. Reference numeral 20 denotes a charging terminal, which is similarly brought into pressure contact with the electrode of the varistor element 16 located at the other end. 21 is a ground lead wire, 22 is a tank, 23 is a charging lead wire, 24 is an insulating plate, 26 is a high voltage lead wire, 26
is the transformer core, 27 is insulating oil, and these correspond to the conventional grounding lead a8, tank 9, charging lead wire 1o, insulating plate 11, high voltage lead wire 12, transformer core 13, and insulating oil 14, respectively. It is something.

28 is an L-shaped metal fitting, one side of which is fixed onto the iron core 26;
The other end is connected to the discharge gap 16h- and the ground terminal 19. 29 is an intermediate terminal pulled out from the middle of the varistor element 16, 3o is an intermediate lead wire connecting this intermediate terminal 29 and a tap terminal 32, which will be described later, and 31 is a winding of a transformer described in circuit terms, with one end is connected to a high voltage lead wire 26 on an insulating plate 24. A tap terminal 32 is drawn out near the beginning of the winding 31 and is connected to the intermediate terminal 29 on the insulating plate 24. Here, the extension of the intermediate terminal 29 and the tap terminal 32 is adjusted to the electrical characteristic ratio of the varistor element 15 and the winding 31, respectively.

Next, the operation of the lightning arrester configured as above will be explained. Now, as in the conventional example, if a surge voltage or short-time AC overvoltage occurs continuously or for a long time, the element temperature of the varistor element 16 becomes extremely high due to the absorbed energy, as in the conventional example. However, heat radiation from each varistor element 16 is uniformly performed directly to the insulating oil 27 in the tank 22, and the insulating oil 27 exposed to high temperature
The specific gravity of the varistor element 16 becomes lighter from the bottom to the top.
A band-shaped flow of insulating oil 27 is formed along the outer surface of the insulating oil 27. Further, this band-shaped flow has a characteristic that the higher the temperature rise of the varistor element 16, the faster the flow becomes. In this way, the heat dissipation effect of the varistor element 16 is greatly improved,
The temperature rise of the varistor element 16 can be suppressed to a low level,
As a result, good thermal stability can be obtained, such as being able to avoid thermal runaway of the lightning arrester in the rated AC application state. Further, it has the effect of reducing characteristic deterioration due to heat generation of the varistor element 16, and also has economical effects such as a simple structure and a small number of parts.

Further, the potential of the tap terminal 32 at the end of the winding 31 is forcibly lowered by the intermediate terminal 29 of the varistor element 15, and the potential gradient within the winding 31 is made uniform, and as a result, steep surge voltages are However, the protective effect of interlayer insulation is high. Furthermore, since the discharge gap 16 is connected in series with all the ground terminals, the operation start voltage of the varistor element 16 can be set low.
Therefore, the limiting voltage is also low.

In addition, the varistor element 16 between the charging terminal 20 and the intermediate terminal 29 operates even against a surge voltage that does not reach the discharge starting voltage of the discharge gap 16, and the end of the winding 31 is protected. It is.

Next, a second embodiment of the present invention will be described with reference to FIG. The difference from the embodiment shown in FIG. 1 is that two lightning arresters of the present invention are combined into one metal unit. In FIG. 2, M and B are respectively 1. The second lightning arrester, 33, both lightning arresters, B
, 34.35 is the charging terminal and intermediate terminal of the lightning arrester B, and 36.37 is the charging terminal and intermediate terminal of the lightning arrester B.

FIG. 3 shows a circuit diagram when the lightning arrester shown in FIG. 2 is connected to a transformer.

Here, the basic operation is the same as in the first embodiment, but
Generally, two lightning arresters are used for the built-in transformer type, but as shown in Figure 2, one lightning arrester is used. By combining the second lightning arrester M, B, it is possible to achieve a compact and economical configuration.

In the embodiment of the present invention, the main body of the lightning arrester is located on the iron core 26, but the same effect can be obtained even if the insulating rod 17 is attached to the tank 22 and the present lightning arrester is attached to the inner surface of the tank 22. Needless to say. Further, in this embodiment, the mounting is done horizontally, but this also applies to mounting diagonally or vertically. Furthermore, the case has been described in which the intermediate terminal 29 is connected to the tap terminal 32 pulled out from near the beginning of the winding 31, but in this case, the tap terminal pulled out from near the end of the winding 31 is connected to the corresponding intermediate terminal. It may also be possible to connect it to

Effects of the Invention As described above, according to the present invention, a cylindrical varistor element and a discharge gap are fixed together with an insulating rod extending from a power equipment, electrical terminals are taken out from both ends and the middle, and these are connected to the electrical equipment. By connecting the end of the winding of the varistor to the ground and the tap terminal in the middle of the winding, the insulating oil in the tank of the power equipment comes into direct contact with the varistor element.
It can quickly dissipate the Joule heat generated within the varistor element and suppress the temperature rise of the varistor element, ensuring good thermal stability of the lightning arrester and suppressing deterioration of the characteristics of the varistor element. It is. In addition, even against steep wave surge voltage, the potential gradient within the winding is made uniform,
This also has the effect of realizing economical manufacturing of lightning arresters. Furthermore, the limiting voltage as a lightning arrester is low, and discharge due to unnecessary short-term AC overvoltage is suppressed, while the winding end is protected by a varistor element against surge voltage that does not activate the discharge gap. It also has

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing a lightning arrester according to an embodiment of the present invention;
Figure 2 is a schematic sectional view showing a lightning arrester according to a second embodiment of the present invention, Figure 3 is a circuit diagram showing the connection when the lightning arrester of Figure 2 is connected to a transformer, and Figure 4 is a conventional lightning arrester. FIGS. 5a and 5b are diagrams illustrating the potential gradient of the lightning arrester shown in FIG. 4. 15... Varistor element, 16... Discharge gap, 16 &... Discharge gap portion, 16b
, 16C...tube, 17...insulation rod, 1
8...nut, 19...ground terminal, 2
0...Charging terminal, 21...Grounding IJ
+ lead wire, 22...tank, 23...charging lead wire, 24...insulation plate, 26...
・High voltage lead wire, 26... Iron core, 27...
...Insulating oil, 28...Metal fittings, 29...
Intermediate terminal, 3o... Intermediate lead wire, 31...
...Winding, 32...Tap terminal. Name of agent: Patent attorney Toshio Nakao and 1 other person (3)
---Balinu Element 23--One charge sort 7 points 1
7- Hokkaido Zelkova 27- Insulating oil/8-7-y 7- 4-112ノ ---・
Ukango right otsusu-) Go, speed, 3/-A east, o-
22--One tank 32- Dasobu shoulder first
Figure 2 Figure 3 Figure 4 Figure 5

Claims (1)

[Claims] A cylindrical varistor element made by stacking a plurality of insulating rods in series extending from a part of a power device having a winding, and a hollow part of each of the discharge gaps provided in series at one end of the varistor element. , the varistor element and the discharge gap are fixed by pressure contact, a charging terminal is connected from the open end of the varistor element connected in series, a ground terminal is connected from the open end of the discharge gap, and a ground terminal is connected from the open end of the varistor element connected in series. Intermediate terminals are taken out from the middle part, the charging terminal is connected to one end of the winding of the power equipment, the grounding terminal is connected to the earth, and the intermediate terminal is pulled out from near the beginning or end of the winding. 1. A lightning arrester characterized in that the lightning arrester is connected to a tap terminal of a power equipment, and is configured such that the varistor element and the discharge gap are in direct contact with insulating oil in a tank of power equipment.