HUT69281A - Monolith lightning arrester of high tensile stress - Google Patents

Abstract

The invention relates to monolith lighting arrester with high tensile strength and without inside gas room, limiting over voltage especially on outdoor electrical networks which is made of flexible insulating material surrounding ZnO varistors (3). The essence of the invention lies in that the ZnO varistors (3) are ring-shaped and attached to an electrical insulating bar (2) so that metal discs (4) ensuring good electrical conductivity are between the ZnO varistors (3) and armatures (1) located on the ends of the electrical insulating bar (2) are made of metal.

Description

DISCLOSURE '

COPIES

SERVICE INVENTION

Furukawa Electric Institute Of Technology Ltd

-INfl 158 Budapest, Késiaé-pk — lu — 10. - Ή L (

inventors:

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Pál Szaplonczay trick. mixed foods - 1424 Bp. KosztaJ.u.31. 30% Marton Téggus oki.gépészmérnök 1061 Bp. Andrássy u.3. 30% Ryuzo Kimata who is he. he is a civil engineer 1H2 Bp. 19 at Vadon. 30% Alajos Bognár k ~ l. electric engineer 1032 Bp. • Ki se e 11 i u .7 7. 10%

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Filed on: 1993 ekt-he ^ & r- 13.

High tensile strength, monolithic surge arrester

FIELD OF THE INVENTION The present invention relates to a high tensile, non-gaseous, monolithic surge arrestor, especially for outdoor power networks, which consists of a resilient insulating material which hermetically seals ZnO varistors. The metal reinforcements that hold the structure together have given the surge arrester a large design at both ends of this surge arrester glass-epoxy rod, which provides tensile strength and is thus suitable for the task of a network tension insulator.

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- 2 Metal oxide surge arresters have been used in electrical networks since 1976. These arresters replaced the conventional spark arresters in high-voltage networks. The metal oxide varistors themselves were developed in Japan in 1968. With the proliferation of cable assemblies and composite insulators, the idea came to provide surge arresters with plastic housings instead of porcelain. This resulted in easier handling, less risk of breakage and increased reliability.

The ZnO rings used in this surge arrester according to the invention are capable of maintaining their electrical performance (low leakage current, low ohmic loss, low residual voltage, high current surge stability, high energy absorbing capacity), i.e., the surge arrester only needs direct lightning replaced. The ZnO rings and the embedded, preferably silicone, elastomeric insulating material provide durable electrical strength, excellent field resistance and high resistance to lubrication. While durable tensile strength or the mechanical lifetime of the outdoor composite insulators is proven by the proven glass-epoxy rod. The monolithic surge arrester, which is sealed and sealed with the aid of a pressurized silicone elastomer (see also Hungarian Patent No. 194,293), cannot be penetrated by moisture and is thus explosion-proof under short-circuit conditions.

As a result of a laboratory arc short circuit simulating catastrophic failure, the direction of the electric arc in the annular geometry patches (as the electric arc was quasi-widening) caused the silicone jacket to puncture, but the glass-epoxy was completely pierced. as a result of the bursting - explosion - of broken ZnO rings - · ··· ····························································································· · the silicone jacket prevented it. This destruction test proves well that the glass-epoxy rod (as it remained intact) is capable of holding the wire, that is, as a tensioner, to continue working.

The high tensile monolithic surge arrester of the present invention, due to its above-described property, can also be installed in place of network insulators, e.g. the size of the network layout before the transformers can be reduced

- Compacting - The surge arrester can be brought closer to the transformer you want to protect without the need to install a separate bracket. It follows from the foregoing that, by means of the present invention, it is safer and more compact in electrical design compared to conventional solutions and in a compact design. with less tension insulators and brackets, more economical surge arresters can be installed.

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Several solutions are known to accomplish the tasks outlined above. A solution is known (eg patent number H 01C7 / 12 .....), where at least two insulating press members are provided on two sides beside the varistor material tablets. These rigid plastic strips are described in detail in the above invention. The tensile strength required for the tension insulators cannot withstand. The above construction can be used only to a small extent for bending, so it is not possible to fasten it as support insulator.

This type of surge arrester requires a separate cantilever rack, which is expensive and does not fit the needs of modern compacting.

The patent in question, since it does not use a spring-loaded rolling element, does not subject the varistor tablets to continuous pressure, so that they cannot be electrically contacted.

A further disadvantage of the construction is that the clamping strips on both sides of the varistors do not provide uniformity to the structure, which also impedes satisfactory contact between the varistors under different temperature conditions.

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It is an object of the present invention to provide an inner gas-free surge arrestor with a core of a high-strength insulating rod which can be fitted with metal reinforcements at the ends of the insulating rod, which structure is durable. to withstand tensile stress, the ZnO varistors around the insulating rod should be embedded in a resilient plastic - lunk-free - which would adhere well to the ZnO varistor, insulating rod and metal fittings, and would resist well to the electric arc and / or. for outdoor use.

The object of the present invention has been achieved by using a surge arrester according to the invention by kneading the ZnO varistors, by placing the ZnO varistors on a electrically insulating rod, by inserting metal disks which provide good electrical contact between the ZnO varistors and spring was reinforced. At the ends of the electrically insulating rod, metal reinforcements were pressed and the structure thus formed was placed in a heated mold, which was pressed under vacuum and overpressure with a liquid casting compound, which filled the cavities without gaps and then cured to a resilient rubbery state.

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The high tensile strength monolithic surge arrester of the present invention, without internal gas space, is particularly suitable for limiting overvoltages in outdoor power networks. This surge arrester consists of a resilient insulating material that hermetically seals the ZnO varistor, where the ZnO varistors are annular and are electrically insulated on an electrically insulating rod. Among the ZnO varistors are metal discs that provide good electrical contact, and the armature at the ends of the electrically insulating rod is made of metal. The ZnO varistors are compressed with constant force by at least one spring.

No. At least one of the reinforcements (1) of the high-tensile compact surge arrestor of FIG. 1B is made of metal material, the metal armature has sealing surfaces connected to the one-piece electrically insulating bar (2), the stacked ZnO varistors (3) have an annular configuration. between the varistors are metal discs (4) which provide good electrical contact, ZnO varistors and A1 discs are compressed by at least one spring (5), and there is a layer (7) connecting the peripheral surfaces of the ZnO varistors (3) and the electrically insulating bar. The elements 3,4 and 5 are embedded in a hermetically sealing electrically insulating casting compound (6).

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The advantage of this surge arrester according to the invention is that it can be used as a dual-function element in the electric network, such as surge arrester and tensile insulator, in that the tensile insulating rod and ZnO varistors are wrapped in a stretchable, flexible plastic , which plastic is able to follow the bar dilatation.

A further advantage is that the surge arrestor according to the invention has a so-called so-called. monolithic. In the event of a direct lightning strike (catastrophe), the electric arc causes the ring-shaped ZnO varistors to crack without breaking the inner insulating rod, which is still resistant to tensile stress, and the flexible embedding material does not allow the ZnO varistors to fly away. it is explosion-proof, ie it does not endanger the environment. A further advantage is that the insulating rod, metal reinforcements and ZnO varistors have on their peripheral surfaces an adhesive which chemically binds the embedded casting compound to the above components. Consequently, moisture penetration is prevented even at extreme temperatures of -50 to +150 ° C.

Another advantage of the vacuum and overpressure is that the embedded casting compound, cured in a hot mold, has no lumps or micro-cracks, so that the electric field does not cause partial discharges or internal ionization. The surge arrestor thus produced is reliable and has a lifetime of at least 25 years.

Claims (2)

Requirements: 1.) For limiting overvoltages of high tensile strength, without internal gas space, for monolithic surge arresters, especially in outdoor power networks, which consists of a resilient insulating material that hermetically seals ZnO varistors, characterized in that the ZnO varistors (3) are knurled ZnO varistors (3) are pegged onto an electrically insulating rod (2), metal discs (4) providing good electrical contact between the ZnO varistors (3), reinforcements (1) at the ends of the electrically insulating rod (2) 2.) Claim 1) surge arrester according to The ZnO varistors (3) are held in constant compression. with forcibly well analyzed, at least one that spring the (5) 3.) It is 1.) obsession 2. ) of excess voltage -levezető characterized in that electrically insulating rod (2) two at the end of there are sealing surfaces. 4.) The 1st), 2.) or 3.) Any one of claims of excess voltage -levezető characterized in that the ZnO varistors (3) and the electrically insulating rod (2) a circumferential surface having an associated layer (7).