On-site dielectric diagnostics of power cables using the isothermal relaxation current measurements

Abstract

The destruction free determination of the ageing status of a polymeric cable insulation is a significant issue in the assessment of the cable residual life. Ageing of apolymer changes the electrical, physical, mechanical and morphological properties of the insulation. Using the computer aided lsothermal-Relaxation-Current-Analysis (IRCAnalysis) the depolarization after dc poling of the insulation is measurable and the separation of different time dependant relaxation mechanisms is feasible. The machine intelligent diagnostic tools for the ageing classification and the residual strength prognosis of installed mediumvoltagecable is described. Withthecalibrationperformed inthe field at one of the major German cable manufacturers using destructive methods (voltage and water tree tests) and the development of the machine intelligent diagnostic software, a non-destructive test procedure for already installed XLPE cable systems is created. The diagnosis reliability ofthe IRC-Analysis based on several on-site tests is also discussed.

Electrical characterization of polymer matrix — TiO2 filler composites through isothermal polarization / depolarization currents and I–V tests

“…(1) and (3)) while the intermediate times were fitted as the sum of three exponential decays (Eq. (2)) [10][11][12][13][14]. In all cases, when using -the Jonscher depolarization model, the short depolarization times were limited in the first 2 s to 5 s approximately while the long depolarization times were assumed to exceed 10 3 s. Figure 3 shows a representative IDC curve fitted according to Eqs.…”

“…In this direction, time domain analysis of depolarization or decay current processes may provide valuable information regarding their dielectric response. The time dependent relaxation process that follows a sudden removal of a polarization field, may be considered as a succession of stages dominated by different time constants [6][7][8][9][10][11][12][13]. The occurrence of polarization/depolarization procedures with different time constants or relaxation times is attributed to the presence of different relaxation processes (multi-stages).…”

“…During this period of time the traps excited by the applied polarization are released and thus, the electric current I decreases monotonically [6][7][8][9][10][11][12][13][14]. This behaviour depends upon various mechanisms, each one corresponding to different time components [10][11][12][13].…”

Application of Particle Swarm Optimization to the Reliability Centered Maintenance Method for Transmission Systems

“…Isothermal relaxation current analysis is a non-destructive method that determines the aging status of a dielectric. The insulation status can be determined by measuring the relaxation current in the time domain [10].…”

Generalized Reliability Centered Maintenance Modeling Through Modified Semi-Markov Chain in Power System

“…It is a destruction-free method for determining the aging status of a dielectric. The insulation status can be determined by measuring the relaxation current in the time domain [8].…”