Cole-cole diagram as diagnostic tool for dielectric liquids

Abstract

Dielectric subsystems have an important influence on reliability, lifetime and power of electrical equipments. Study of dielectric parameters and their changes due to degradation mechanisms provide important information about the equipments. Paper deals with oil-paper systems and their thermal degradation. These systems are used for example in transformer, capacitors and bushings. Thermal degradation causes increasing of moisture content thus number of polar particles. Therefore the main idea of this paper is diagnostic of oil-paper insulation based on a method of polarization measurement. One of the methods is Cole-Cole diagram [I] or its modification e.g. Davidson [5], Havriliak-Negami [11]. The next aim of the paper is measurement of the system parameters (Complex permittivity, Viscosity, Acid value, Resistivity, Polarization index and Dissipation factor) and their changes due to thermal degradation. In experiments are used a normal and an environmental friendly fluid.

Application of Cole–Cole model to transformer oil‐paper insulation considering distributed dielectric relaxation

“…Normalising total equilibrium susceptibility χ ot = 1, real and complex susceptibilities in discrete form can be obtained numerically from known set of values of discrete frequency distribution function (ν k , F k ) using modified forms of (25) and (26) as:…”

“…Such a diagram is the plot between real and imaginary components of complex permittivity (ε′ and ε″) with frequency as the running parameter. Cole-Cole plots have thenceforth been used by researchers for characterising different materials and composites including dielectric mixtures [21], ferrite films [22], ionic liquids [23], cable insulating oil [24], polar liquids [25], dielectric liquids [26] etc. Initial attempts for analysing dielectric response measurement results of transformer oil-paper insulation with Cole-Cole model were carried out by S. Wolny et al [27][28][29].…”