Electrical insulation

New development today lead to an increase of dielectric performance of the insulation.

The increase in operating frequency causes accelerated aging.

The life of insulation also requires an improvement .

These new needs are growing day by day at the moment when the conversion of energy is undergoing a revolution.

PARTIAL DISCHARGE

« CORONA » EFFECT

Partial discharges are a consequence of a stress in a dielectric insulation during the high voltage application in high frequency. The causes are of several kinds, among which the not homogeneous distribution of the electric field, the presence of bubbles within the insulation, the effect of spikes on the insulating material, the presence of moisture or cracks, the presence of surface contaminants insulators.

Partial discharges are present at insulation defects on Litz cables and junctions of the cables in the electrical hight voltage equipment in rotating machines (asynchronous & synchronous machines …) and transformers, or in industrial devices such as power switching systems (power supplies).

The aim of these measures is the establishment of test campaigns for the purpose of safety and preventive maintenance or for the qualification of finished products after manufacture.

The "corona" effects appear on  a high electrical potential conductor. The electric field in the vicinity there of may become intense enough to cause ionization of air molecules. It causes a chemical decomposition causing erosion and deterioration of the metal surfaces. This phenomenon is called "corona effect"  and is still characterized by a bluish tint rich in ultraviolet around the conductors and sometimes emits an audible sound to the ear. One consequence of this is the loss of energy in electricity grids and reducing the lifetime of the insulation.

TEST RESOURCES

STANDARD

Find the list of applicable standards for these tests on the catalog LABORATORY

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