Varistor surge arrestors, in particular for high tension

A surge arrestor comprising:

• a stack of varistors;
• a first envelope of composite material comprising fibers impregnated by a resin formed on the stack of varistors said first envelope being at least semi-rigid and having constant outside section over its length, to compensate for surface non-uniformities in the stack of varistors due to defects of alignment and to dispersions in dimensions of the varistors;
• and
• a finned external envelope placed on the first envelope made of composite material;
• the finned external envelope comprising firstly an outer envelope of substantially constant thickness formed by extrusion on the first envelope, and secondly annular fins subsequently installed on the outer envelope after the outer envelope has been extruded.

A surge arrestor comprising:

• a stack of varistors;
• a first envelope of composite material comprising fibers impregnated by a resin formed on the stack of varistors said first envelope being at least semi-rigid and having constant outside section over its length to compensate for surface non-uniformities in the stack of varistors due to defects of alignment and to dispersions in dimensions of the varistors;
• a keying primary coat on outside surface of the first envelope, and
• a finned external envelope placed on the first envelope made of composite material;
• the finned external envelope comprising firstly an outer envelope of substantially constant thickness formed by extrusion on the first envelope, and secondly annular fins subsequently installed on the outer envelope after the outer envelope has been extruded.

A method of making a surge arrestor comprising the following steps:

• i) stacking a stack of varistors;
• ii) forming a first envelope of composite material comprising fibers impregnated by a resin on the stack of varistors, said first envelope being at least semi-rigid and having constant outside section over its entire length, to compensate for surface non-uniformities in the stack of varistors due to alignment errors and to dispersions in dimensions of the varistors;
• and
• iii) placing an outer envelope having fins on the first envelope made of composite material;
• by
• a) initially extruding an outer envelope of substantially constant thickness over the first envelope;
• and then
• b) fitting annular fins to the outer envelope after the outer envelope has been extruded, wherein the outer envelope is at least 3 mm thick.

A method of making a surge arrestor comprising the following steps:

• i) stacking a stack of varistors;
• ii) forming a first envelope of composite material comprising fibers impregnated by a resin on the stack of varistors, said first envelope impregnated by a resin on the stack of varistors, said first envelope being at least semi-rigid and having constant outside section over its entire length, to compensate for surface non-uniformities in the stack of varistors due to alignment errors and to dispersions in dimensions of the varistors;
• and
• iii) placing an outer envelope having fins on the first envelope made of composite material;
• by
• a) initially extruding an outer envelope of substantially constant thickness over the first envelope;
• and then
• b) fitting annular fins to the outer envelope after the outer envelope has been extruded, and fixing said fins on the outer envelope by means of a synthetic adhesive.

A method of making a surge arrestor comprising the following steps:

• i) stacking a stack of varistors;
• ii) forming a first envelope of composite material comprising fibers impregnated by a resin on the stack of varistors, said first envelope being at least semi-rigid and having constant outside section over its entire length, to compensate for surface non-uniformities in the stack of varistors due to alignment errors and to dispersions in dimensions of the varistors;
• and
• iii) placing an outer envelope having fins on the first envelope made of composite material;
• by
• a) initially extruding an outer envelope of substantially constant thickness over the first envelope;
• and then
• b) fitting annular fins to the outer envelope after the outer envelope has been extruded wherein the envelope of composite material comprises a cloth of fibers extending parallel to a stacking axis of the varistors, and that means are provided suitable for locking the envelope of composite material both in rotation and in translation to contact pieces placed at ends of the stack of varistors.

A method of making a surge arrestor comprising the following steps:

• i) stacking a stack of varistors;
• ii) forming a first envelope of composite material comprising an open-mesh fiber cloth impregnated by a resin on the stack or varistors, said first envelope being at least semi-rigid and having constant outside section over its entire length, to compensate for surface non-uniformities in the stack of varistors due to alignment errors and to dispersions in dimensions of the varistors;
• and
• iii) placing an outer envelope having fins on the first envelope made of composite material;
• by
• a) initially extruding an outer envelope of substantially constant thickness over the first envelope;
• and then
• b) fitting annular fins to the outer envelope after the outer envelope has been extruded.

A method of making a surge arrestor comprising the following steps:

• i) stacking a stack of varistors;
• ii) forming a first envelope of composite material comprising fibers impregnated by a resin on the stack of varistors, said first envelope being at least semi-rigid and having constant outside section over its entire length, to compensate for surface non-uniformities in the stack of varistors due to alignment errors and to dispersions in dimensions of the varistors;
• and
• iii) placing an outer envelope having fins on the first envelope made of composite material;
• by
• a) placing a keying primary coat on outside surface of the first envelope
• b) initially extruding an outer envelope of substantially constant thickness over said keying primary coat;
• and then
• c) fitting annular fins to the outer envelope after the outer envelope has been extruded.

A method of making a surge arrestor comprising the following steps:

• i) stacking a stack of varistors;
• ii) forming a first envelope of composite material comprising fibers impregnated by a resin on the stack of varistors, said first envelope being at least semi-rigid and having constant outside section over its entire length, to compensate for surface non-uniformities in the stack of varistors due to alignment errors and to dispersions in dimensions of the varistors;
• iii) fixing a bar centered on an axis of the stack and having the same outside section as the first envelope on at least one of ends of the stack of varistors fitted with the first envelope, and
• iv) placing an outer envelope having fins on the first envelope made of composite material;
• by
• a) initially extruding an outer envelope of substantially constant thickness over the first envelope;
• and then
• b) fitting annular fins to the outer envelope after the outer envelope has been extruded.

A surge arrestor comprising:

• a stack of varistors;
• a first envelope of composite material comprising fibers impregnated by a resin formed on the stack of varistors said first envelope being at least semi-rigid and having constant outside section over its length to compensate for surface non-uniformities in the stack of varistors due to defects of alignment and to dispersions in dimensions of the varistors;
• and
• a finned external envelope placed on the first envelope made of composite material;
• and
• the finned external envelope comprising firstly an outer envelope of substantially constant thickness formed by extrusion on the first envelope, and secondly annular fins subsequently installed on the outer envelope after the outer envelope has been extruded, wherein the outer envelope is at least 3 mm thick.

A surge arrestor comprising:

• a stack of varistors;
• a first envelope of composite material comprising fibers impregnated by a resin formed on the stack of varistors said first envelope being at least semi-rigid and having constant outside section over its length to compensate for surface non-uniformities in the stack of varistors due to defects of alignment and to dispersions in dimensions of the varistors;
• and
• a finned external envelope placed on the first envelope made of composite material;
• and
• the finned external envelope comprising firstly an outer envelope of substantially constant thickness formed by extrusion on the first envelope, and secondly annular fins subsequently installed on the outer envelope after the outer envelope has been extruded and fixed on the outer envelope by means of a synthetic adhesive.

A surge arrestor comprising:

• a stack of varistors;
• a first envelope of composite material comprising a cloth of fibers extending parallel to an axis of the stack of varistors impregnated by a resin formed on the stack of varistors said first envelope being at least semi-rigid and having constant outside section over its length to compensate for surface non-uniformities in the stack of varistors due to defects of alignment and to dispersions in dimensions of the varistors;
• means are provided suitable for locking the envelope of composite material in rotation and in translation on contact pieces placed at ends of the stack of varistors, and
• a finned external envelope placed on the first envelope made of composite material;
• and
• the finned external envelope comprising firstly an outer envelope of substantially constant thickness formed by extrusion on the first envelope, and secondly annular fins subsequently installed on the outer envelope after the outer envelope has been extruded.

A surge arrestor comprising:

• a stack of varistors;
• a first envelope of composite material comprising an open-mesh fiber cloth impregnated by a resin formed on the stack of varistors said first envelope being at least semi-rigid and having constant outside section over its length to compensate for surface non-uniformities in the stack of varistors due to defects of alignment and to dispersions in dimensions of the varistors;
• and
• a finned external envelope placed on the first envelope made of composite material;
• and
• the finned external envelope comprising firstly an outer envelope of substantially constant thickness formed by extrusion on the first envelope, and secondly annular fins subsequently installed on the outer envelope after the outer envelope has been extruded.

A surge arrestor comprising:

• a stack of varistors;
• a first envelope of composite material comprising fibers impregnated by a resin formed on the stack of varistors said first envelope being at least semi-rigid and having constant outside section over its length to compensate for surface non-uniformities in the stack of varistors due to defects of alignment and to dispersions in dimensions of the varistors;
• and
• a finned external envelope placed on the first envelope made of composite material;
• and
• the finned external envelope comprising firstly an outer envelope of substantially constant thickness formed by extrusion on the first envelope, and secondly annular fins subsequently installed on the outer envelope after the outer envelope has been extruded and collars clamped on ends of the outer envelope.

A surge arrestor comprising:

• a stack of varistors;
• a first envelope of composite material comprising fibers impregnated by a resin formed on the stack of varistors said first envelope being at least semi-rigid and having constant outside section over its length to compensate for surface non-uniformities in the stack of varistors due to defects of alignment and to dispersions in dimensions of the varistors;
• and
• a finned external envelope placed on the first envelope made of composite material;
• and
• the finned external envelope comprising firstly an outer envelope of substantially constant thickness formed by extrusion on the first envelope, and secondly annular fins subsequently installed on the outer envelope after the outer envelope has been extruded and
• including furthermore a contact piece at each end of said stack of varistors, that has an annular groove designed to receive one end of the envelope of composite material together with a band clamping said envelope in the groove, and a structure that is not circularly symmetrical about the axis of the contact piece.