Effect of thermal transient on the polarization and depolarization current measurements

On the Feasibility of Using Poles Computed from Frequency Domain Spectroscopy to Assess Oil Impregnated Paper Insulation Conditions

“…The DDF of a dielectric material is a complex function of at least two variables-frequency and temperature, although aging, moisture and pressure may be other physical variables [4][5][6][7][8][9][10][11][12][13][14][15][16]. A complete representation should therefore be "three-dimensional" plots, but these are cumbersome and are therefore seldom employed, although modern computer graphics enable one to plot third-angle projections in two dimensions.…”

“…These pressboard samples were carefully dried under vacuum (<1 mbar, 48 h at 110 °C) before impregnation, with a degassed and dehumidified commercial grade mineral oil sample. The degasification and dehumidification took place in a two stage dehydrating and degassing column [6,15]. This procedure allowed reducing the moisture content in the oil from 18 to 5 ppm and from 6 to 1% in the pressboard.…”

“…Over the last decades, the increasing requirements for appropriate tools to diagnose power equipments insulation non-destructively and reliably in the field drive the development of diagnostic tools based on changes of the dielectric properties of the insulation. Among these tools time domain measurement based on Polarization/Depolarization Current (PDC) and Frequency Domain Spectroscopic (FDS) measurements are gaining exceptional importance to the utility professionals [7][8][9][10][11][12][13][14][15]. The FDS is the favoured choice for on-site measurements due to its robustness against noise.…”

“…The FDS is the favoured choice for on-site measurements due to its robustness against noise. In the last decades, much study and work has been performed with the aim of improving our basic understanding of dielectric response interpretation schemes (e.g., [2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21]). It is now accepted that Frequency Domain Spectroscopy (FDS) measurement techniques provide indication of the general ageing status and moisture content of the oil-paper insulation of transformer.…”

A New Method for Evaluating Moisture Content and Aging Degree of Transformer Oil-Paper Insulation Based on Frequency Domain Spectroscopy

“…Various methods have been developed to help to evaluate the condition of the insulating paper, including the breakdown voltage, the tensile strength, the degree of polymerization and Karl Fischer coulometric titration [9,10]. More recently, Frequency Domain Spectroscopy (FDS) [11][12][13], Polarization and Depolarization Current (PDC) [14][15][16] and Recovery Voltage Measurement (RVM) [17], which are based on dielectric response, have become a hotspot for scholars to study because of easy operation and no need for sampling. Compared with PDC and RVM, FDS has the advantages of rich insulation information and strong anti-interference ability, so it has great potential in oil-paper insulation condition evaluation [18].…”