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February 4, 2017

Insulators tested in vertical position and horizontal position

As we know,high voltage insulators shall subject to mechanical failing load test, and when we mention “test in vertical position and horizontal position”, this more refer to suspension insulator, tension insulator, post insulator and pin insulator. The suspension and tension insulator are normally tested in horizontal direction, as they are long in shape, with length up to 3-5 meters for 400KV and below, these insulators are tested in horizontal tensile testing machine on the ground. Such tests comply with real environment of suspension/tension insulators on overhead lines as most of them are in horizontal direction. While for post insulator and pin insulator, for example, 11kv and 33kv pin insulators, these insulators are often vertically mounted on wooden crossarms to bear certain cantilever load of cables and conductors, and for power substations, high voltage post insulators are also in vertical direction. And these insulators shall be tested in vertical direction with a pushing strength from horizontal direction to test their cantilever failing load. There are railway crossarm insulator as well, even though they are not used 100% vertically or horizontally, but tests of railway crossarm insulators shall subject to test of post insulators in vertical direction with bending&torsion testing machine.

 

We have talked about mechanical failing load of insulators,here we have a document of an India project of insulators, let’s see how they define high voltage test of insulators tested in vertical position and in horizontal position:

INSULATORS TESTED IN VERTICAL POSITION

The insulators shall be hung vertically from an earthed support by means of a wire rope or metal rod, The distance between the top of the insulator metal fittings and the point of support shall be not less than 1 meter. At the lower end of the insulator shall be attached, if required, a metallic rod of weight adequate to ensure that the insulator remains the vertical position during test.

No subject shall be nearer to the axis of the insulator less than 1 meter or 1.5 times the length of the insulator whichever is the greater.

Test voltage shall be applied between the metal rod at the bottom of the insulator and the earthed point of suspension.

INSULATOR TESTED IN HORIZONTAL POSITION

The insulator shall be anchored by means of a cable or metal rod connected to earth. The distance between the top of the insulator metal fitting and the point of anchorage shall be not less than 1 meter.

The other end of the insulator shall be provided with a metal rod of about 1 meter long and the whole arrangement maintained in an approximately horizontal position by any convenient means.

No subject shall be nearer to the axis of the insulator less than 1 meter or 1.5 times the length of the insulator whichever is the greater.

The test voltage shall be applied between the end of the metal rod and the earthed point of anchorage.

Electrical insulators, Insulator testing machines, Polymer insulators
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