Surge arrester with external short-circuit device

Details Surge arrester with external short-circuit device Surge arrester with external short-circuit device

1995-10-30

1997-07-01

Gaffin, Jeffrey A.

Electricity: electrical systems and devices

Safety and protection of systems and devices

High voltage dissipation

361129, 361124, 337 32, H02H 906

Patent

active

056444656

DESCRIPTION:

BRIEF SUMMARY
BACKGROUND OF THE INVENTION

The present invention concerns the field of electric components and is intended for use in designing a gas-filled three-electrode surge arrester equipped with an external short-circuit device. Such a short-circuit device is used to protect the surge arrester in the event of a long-time load. As a rule, such a short-circuit device has a component that melts at high temperatures and short-circuits the center electrode and one or both of the end electrodes.
With a known three-electrode surge arrester of this type, the outside short-circuit device consists of a two-arm spring clip, arched in a roof-shaped manner, that extends in the axial direction of the surge arrester, where its arms form an obtuse angle and its free ends are in contact with the end electrodes with a meltable layer of insulation in between. The outermost ends of the two arms are bent slightly so that these ends run parallel to the axis of the surge arrester and consequently are in contact with the outer peripheral surface of the end electrodes. With this known short-circuit device, the spring clip is provided with a passage in the middle through which it is attached to the radially projecting connecting wire of the center electrode. In this way the spring clip can be attached to the connecting wire with an initial tension as in French patent A 2,625,377.
With another known surge arrester, a two-arm spring clip is attached to the center electrode at the center. The two free ends of the arms of this spring clip are in insulated contact with the outside surfaces of the end electrodes. With this surge arrester, the spring clip serves to create a short-circuit device and also to form parallel spark gaps in air. A layer of insulation 20 to 40 .mu.m thick made of polyurethane varnish, for example, is applied to the ends of the two arms of the spring clip. The middle part of the spring clip is connected to the radially projecting connecting wire of the center electrode as in U.S. Pat. No. 4,912,592.
With yet another known surge arrester, a spring clip is again provided as an external short-circuit device. The arms of the spring clip here project beyond the end electrodes of the surge arrester in the axial direction and their ends are in insulated contact with the end electrodes at the ends, in other words, axially. To secure the wing-like spring clip, it is provided with a passage in the center in the form of a punched-out H shape, and the connecting wire of the center electrode is inserted between the tabs of the H shape. The spring clip is attached to the connecting wire in a prestressed state by means of the springy tabs (WO 90/13904).


SUMMARY OF THE INVENTION

The present invention provides a design of a spring clip for a gas-filled surge arrester. In that design a reliable contact with the end electrodes is assured.
To achieve this object, the free ends of the spring clip in the design according to this invention project axially beyond the end electrodes and are in contact with the peripheral outside edge of the respective end electrode.
With an external short-circuit device of such a design, the arms of the spring clip are in point contact with the end electrodes with a sufficient initial tension. Thus, when the insulation layer melts because the arms of the spring clip are in a point contact with the respective end electrode.
The reliability of a point contact can be increased by providing two straps on the ends of the arms of the spring clip so they are in contact with the peripheral edge of the respective end electrode. This also provides torsional security for the spring clip. Such a design of the spring clip is especially suitable for surge arresters where the connecting wires for all the electrodes run radially in the same direction. The roof-shaped arch in the spring clip is preferably such that the arms form an obtuse angle of about 110.degree.-150.degree. when not under load. The method of securing the spring clip to the center electrode or its connecting wire or terminal pin may be either by means of a

REFERENCES:
patent: 4851957 (1989-07-01), Chung
patent: 4910489 (1990-03-01), Neuwirth et al.
patent: 4912592 (1990-03-01), Flindall et al.
patent: 4984125 (1991-01-01), Uwano
patent: 5027100 (1991-06-01), Neuwirth et al.
patent: 5029302 (1991-07-01), Masghati et al.

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