Title :
On-site diagnosis of power transformers by means of relaxation current measurements
Author :
Houhanessian, Vahe Der ; Zaengl, Walter S.
Author_Institution :
High Voltage Lab., Swiss Fed. Inst. of Technol., Zurich, Switzerland
Abstract :
The purpose of this paper is to show how the relaxation currents of a power transformer can be calculated, when the geometrical configuration of the main insulation and the dielectric properties of its components, oil and pressboard, are known. To model this insulation a simple equivalent circuit is presented, which is derived from basic relations of linear dielectric theory. The dielectric characteristics of oil and pressboard necessary for modelling are determined from dielectric response measurements on samples. Therefore some results of relaxation current measurements of pressboard samples in dependence on moisture content and temperature are presented. Finally, some examples of on-site measurements of relaxation currents on hitherto unused power transformers are shown which are used here to demonstrate how the moisture content of pressboard of these transformers can be quantified from evaluation of their relaxation currents
Keywords :
dielectric relaxation; equivalent circuits; insulation testing; power transformer insulation; power transformer testing; transformer oil; dielectric response; equivalent circuit; geometrical configuration; linear dielectric theory; moisture content; on-site diagnosis; power transformers; pressboard samples; relaxation current measurements; temperature dependence; Current measurement; Dielectric measurements; Dielectrics and electrical insulation; Equivalent circuits; Moisture; Oil insulation; Petroleum; Power transformer insulation; Power transformers; Temperature dependence;
Conference_Titel :
Electrical Insulation, 1998. Conference Record of the 1998 IEEE International Symposium on
Conference_Location :
Arlington, VA
Print_ISBN :
0-7803-4927-X
DOI :
10.1109/ELINSL.1998.704641
