Surge arrester with a mtal oxide resistor

Electricity: electrical systems and devices – Safety and protection of systems and devices – High voltage dissipation

Patent

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Details

361117, 338 21, 338235, H02H 104

Patent

active

055964761

DESCRIPTION:

BRIEF SUMMARY
BACKGROUND OF THE INVENTION

The invention, which is in the area of protective engineering for energy distribution facilities, is concerned with the structural configuration of a surge arrester, with an insulating housing and with a metal oxide resistance arranged inside the insulating housing, such that the metal oxide resistor consists of two or more columns, connected electrically in parallel, made up of a larger number of resistance elements, of which each column has two separate holding plates between which the resistance elements of the column are arranged, and which in turn are joined by means of insulating holding rods which laterally immobilize the resistance elements.
Surge arresters with a metal oxide resistor as the shunting element generally consist of a plurality of flat cylindrical resistance elements arranged in columnar fashion one above the other, the column formed by these resistance elements being arranged inside a ceramic or plastic insulator tightly sealed at the top and bottom ("IEEE Transactions on Power Delivery," Volume PWRD-1, No. 1, January 1986, pp. 151-156; FIG. 6).
To increase the energy handling capacity or to reduce the residual voltage, it is common in the case of metal oxide shunts to connect a plurality of resistance columns made up of individual resistance elements in electrically parallel fashion. For this purpose, two to four columns are arranged next to one another, inside a common insulating housing, on a support plate by means of which they are inserted into the common housing. This is known, for example, from U.S. Pat. No. 4,326,232.


SUMMARY OF THE INVENTION

The invention creates a surge arrester structure which improves the individual columns in terms of handling and accessibility for measurement purposes. Proceeding from a surge arrester with the features of the preamble of claim 1, the columns are arranged at the lower end of the insulating housing on a plate, centered with respect to the axis of the insulating housing, and a separate compression spring is associated with each of the columns for contact purposes.
A configuration of this kind thus provides for each individual column, made up of resistance elements, to constitute an independent module which represents a mechanically self-supporting structure. The particular required number of these modules is placed next to one another in the insulating housing, and mechanically and electrically joined together and immobilized at both ends by suitable structural means. The assembly of multiple modules, standardized in this fashion and completely identical to one another, yields a substantial simplification in production. In particular, the individual modules are easy to handle during assembly of the surge arrester. Furthermore, it is possible to evaluate the individual modules before complete assembly of the surge arrester, and thus determine current distribution. With reference to the operation of this kind of surge arrester, separate construction of the individual resistance columns allows displacement of the modules with respect to one another when the suppressor is overloaded, thus opening up a pressure relief channel of the greatest possible cross section in the region of the active arc. This displaceability can be ensured by suitable structural measures at the top end--and, if necessary, also at the bottom end--of the individual columns.
Because contact with each individual resistance column is made by a separate compression spring, a contact pressure of substantially equal magnitude, and thus a transition resistance of equal magnitude, is achieved for all the modules.


BRIEF DESCRIPTION OF THE DRAWINGS

An exemplary embodiment of the invention is depicted in FIGS. 1 and 2, in which:
FIG. 1 shows a vertical section of the housing with a view of the suppressor element; and
FIG. 2 shows a cross section through the suppressor in the region of the lower end.


DETAILED DESCRIPTION

FIG. 1 shows an surge arrester whose housing consists, in a known manner, of ceramic insulator 1 and a metal foot part 2 and a

REFERENCES:
patent: 4326232 (1982-04-01), Nishiwaki et al.
patent: 4812944 (1989-03-01), Eberhard et al.
patent: 4814936 (1989-03-01), Ozawa et al.
patent: 5113306 (1992-05-01), Veverka et al.
patent: 5359316 (1994-10-01), Ozawa et al.
IEEE Transactions On Power Delivery, vol. PWRD-1, No. 1, Jan. 1986, pp. 151-156, J. Ozawa et al.: Pressure Relief Design and Performance of Metal Oxide Surge Arresters.

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