Open AccessApplication of a simple method for determining the equilibrium resistivity of dielectric luiquids
Author(s) -
Joachim Schiessling,
Nils Lavesson,
Lars Walfridsson
Publication year - 2017
Publication title -
proceedings of the nordic insulation symposium
Language(s) - English
Resource type - Journals
ISSN - 2535-3969
DOI - 10.5324/nordis.v0i25.2363
Subject(s) - electrical resistivity and conductivity , pressboard , dielectric , materials science , transformer , voltage , transformer oil , ohm , condensed matter physics , composite material , electrical engineering , physics , optoelectronics , engineering
For the design of the electrical insulation of an UHVDC (Ultra High Voltage Direct Current) converter transformer the resistivity of the pressboard and mineral oil has to be known. For solid insulation the resistivity is virtually constant, however, in liquids it is dependent on, e.g., applied electric stress and time of electrification. Several methods are discussed in the standards. One way to characterize the oil is the measurement of the equilibrium resistivity, in contrast to an apparent resistivity for oil under high electric stress. Measurements using a low voltage triangular shaped voltage form allow calculation of equilibrium resistivity. The oils investigated show equilibrium resistivity in the range 5E11 Ohm·m to 5.96E12 Ohm·m, which are typical values for transformer oil. There is good agreement between these results and reference measurements using dielectric response