Detection of oil-pressboard insulation aging with dielectric spectroscopy in time and frequency domain measurements

authored by

O. Hassan, Amir Abbas Shayegani Akmal, H. Borsi, Ernst Gockenbach, E. M. Abu-Elzahab, Mahmoud I. Gilany

Abstract

The insulation system of power transformers consists of oil and cellulose, whose dielectric properties are strongly influenced by moisture, temperature and aging. Their condition can therefore, be evaluated using dielectric response measurements. This contribution describes the Return Voltage Measurement (RVM) diagnostic method based on scanning the polarization spectra of the oil-paper insulation in the time range of Is to 1200s at an excitation voltage of 500V (DC). The variation of the dissipation factor (tan 5) and power factor (cos θ) in the frequency range of 0.0001 to 1000 Hz were measured and the effects of moisture and aging were analyzed. Furthermore accelerated aging processes of oil-paper samples were investigated under air environment up to a temperature of 388 K (115°C). Typical transformer proportions of copper, aluminum, zinc and iron were added to oil-paper insulation during the aging process in order to simulate the possible oxidation processes. For the investigation of the long time behavior, the oil-paper insulation samples were aged at different aging times at 250, 500, 1000 and 2000 hours which simulate long time service condition due to the used severe aging conditions.

Organisation(s)

High Voltage Engineering and Asset Management Section (Schering Institute)

External Organisation(s)

Cairo University
University of Tehran
Aswan University

Type

Conference contribution

Volume

2

Pages

665-668

No. of pages

4

Publication date

2004

Publication status

Published

Peer reviewed

Yes

ASJC Scopus subject areas

General Engineering