High-voltage switches with arc preventing or extinguishing devic – Arc preventing or extinguishing devices – Resistance inserting
Patent
1998-11-02
2000-04-11
Donovan, Lincoln
High-voltage switches with arc preventing or extinguishing devic
Arc preventing or extinguishing devices
Resistance inserting
218 7, 361117, H01H 3316
Patent
active
060490497
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a surge arrester comprising an elongated column composed of a number of coaxially arranged valve units, each comprising a stack of a plurality of cylindrical varistor blocks which are arranged one after the other in the axial direction of the varistor blocks between two end electrodes and surrounded by an elongated, electrically insulating outer housing.
The invention is primarily intended for use in surge arresters for relatively high system voltages, for example 420 kV and higher, but it can also be used in arresters for lower voltages.
BACKGROUND ART
Surge arresters for voltages of the of the above-mentioned order of magnitude can be subjected to high mechanical stresses, for example due to wind load and earthquake.
It is known to design surge arresters for high system voltages with a lower part comprising three vertically arranged insulator columns, which are mounted at the bottom on a metal stand intended for ground connection to form, in cross section, an equilateral triangular configuration. The lower part supports a centrally placed upper insulator column, which at the top is provided with an end armature intended for high-voltage connection. Each insulator column is composed of a plurality of coaxially arranged hollow insulators of porcelain. The upper insulator column and one of the insulator columns in the lower part comprise varistor blocks, whereas the other two insulator columns in the lower part are empty and only have a mechanical function. Such an arrester, designed for system voltages of 1600 kV, is shown in Asea Journal 1977, vol. 1, p. 19. This arrester has a height of 13 meters. Such a design is very costly and, in addition, cannot be used without taking special measures if the housings of the valve units are made of polymer material instead of porcelain, because these materials have completely different mechanical properties.
SUMMARY OF THE INVENTION
The present invention aims to provide a surge arrester which is considerably less expensive than comparable prior art designs and which, in addition, is more resistant to mechanical stresses which may arise due to external influence, for example in case of an earthquake.
According to the invention, the stack of surge arresters is mechanically divided into an upper and a lower column part, and the two column parts are connected to each other via a moment-limiting articulated member. The articulated member is made with an upper bearing plate which has a concave sliding surface, which makes contact with a convex sliding surface of a lower bearing plate. The upper bearing plate is connected to the grounded stand of the arrester by means of tensionally prestressed, insulated links. The articulated member includes a spring system adapted to the stiffness of the lower column part to maintain the two bearing plates (and hence the end portions of the two column parts interconnected by the articulated member) positioned correctly relative to each other in the transversal direction.
The shape of the sliding surfaces of the bearing plates is determined by the deflection profile of the arrester column, and, the surfaces exhibit a larger angular change (less radius of curvature) at the periphery than at the center. In such a design, the insulated links take up a larger force relative to the arrester column and this difference increases with the deflection. In this way, the arrester may also withstand very high static and dynamic loads.
BRIEF DESCRIPTION OF THE DRAWINGS
The invention will be explained in greater detail by description of embodiments with reference to the accompanying drawings, wherein
FIG. 1 shows in a side view one embodiment of a surge arrester designed according to the invention, and
FIG. 2 shows in axial section a moment-limiting articulated member included in the surge arrester according to FIG. 1.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
The surge arrester shown in FIG. 1 is intended for a system voltage of 550 kV and has a height of 5 m. The arrester has the shape of an
REFERENCES:
patent: 3586913 (1971-06-01), Olsen
patent: 3856242 (1974-12-01), Cook
patent: 5444429 (1995-08-01), Sakich et al.
Swedish-American UHV Test Station, p. 67/Svenek-amerikanek provningestation for ultrahoga-spanningar, p. 19, ASEA Journal 1977, vol. 1 (no month).
WO 96/07186 7/1996 WIPO Surge Arrester.
ABB AB
Donovan Lincoln
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