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Improved method for incoming goods inspection/partial discharge testing of insulation materials on the basis of PXIPD (Pulsed X-ray Induced Partial Discharges)

IP.com Disclosure Number: IPCOM000202514D
Publication Date: 2010-Dec-20
Document File: 2 page(s) / 27K

Publishing Venue

The IP.com Prior Art Database

Abstract

This patent describes a new process of partial discharge testing of insulation components for gas insulated switchgear that can be used if free electrons in a void which are necessary for the triggering of a partial discharges are generated by pulsed X-rays instead of background radiation or field emission effects on the surface of a void: If the generation of free electrons can be relied on without these effects, the applied voltage during or before a partial discharge measurement can be reduced to voltage levels as applied during service conditions or values slightly above that voltage. In comparison to current standard test procedures, this reduces the electrical stress of the components as well as the costs for a suitable high voltage transformer and it permits to use a gas with a lower dielectric strength than SF6 for the electrical insulation of the device under test. By using a technical gas which is environmentally friendly (examples: helium, nitrogen or compressed air), the testing time for one device under test and the investment costs for a testing facility can be significantly reduced because the technical gas does not have to be treated in a closed cycle which facilitates the gas handling.

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Page 01 of 2

Title: Improved method for incoming goods inspection/partial discharge testing of insulation materials on the basis of PXIPD (Pulsed X-ray Induced Partial Discharges)

Abstract:

This patent describes a new process of partial discharge testing of insulation components for gas insulated switchgear that can be used if free electrons in a void which are necessary for the triggering of a partial discharges are generated by pulsed X-rays instead of background radiation or field emission effects on the surface of a void: If the generation of free electrons can be relied on without these effects, the applied voltage during or before a partial discharge measurement can be reduced to voltage levels as applied during service conditions or values slightly above that voltage. In comparison to current standard test procedures, this reduces the electrical stress of the components as well as the costs for a suitable high voltage transformer and it permits to use a gas with a lower dielectric strength than SF6 for the electrical insulation of the device under test. By using a technical gas which is environmentally friendly (examples: helium, nitrogen or compressed air), the testing time for one device under test and the investment costs for a testing facility can be significantly reduced because the technical gas does not have to be treated in a closed cycle which facilitates the gas handling.

Content:

Voids in electrical insulation materials are the cause for internal partial discharges which trigger erosion processes inside the material. These erosion processes often result in a failure of a complete insulation system. Voids can be detected with the aid of partial discharge measurments which are performed as a part of standard incoming goods inspections and routine tests for gasinsulated switchgear systems.

A partial discharge in a void can only be triggered if the applied electric field strength is high enough AND if a free electron is present in the void (this electron is accelerated in the field and initiates the discharge in form of a cahrge carrier avalanche - as can be seen in the following picture). The electric field is dependent on the high voltage which is applied to the device under test. The free electron is usually generated either by background radiation or by field emission from the surface of the void. The statistical waiting time for a free electron generated by background radiation is highly dependent on the volume of the void and can be in the order of days for voids with a diameter smaller than 1mm.

Gas particle

Acceleration due to electrical Field

Free electron

Ion



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For industrial applications, the partial discharge measurement time is only in the order of minutes. In order to detec...