Investigation of the 'non-linear' dielectric response of water tree-aged XLPE cables in the time and frequency domain

Abstract

Heavily water tree-aged cables show a so-called 'nonlinear' dielectric response with respect to the voltage whose origin is still unknown and which is difficult to relate to the actual condition of the cable insulation. However, the 'non-linear' behaviour is one possible diagnostic criterion. The aim of the work presented in this paper is to investigate this 'non-linear' dielectric response in the time and frequency domain, as well as to correlate both domains by different mathematical approaches. The 'non-linear' behaviour of the dielectric response is found to be differeni in the time and frequency domain. Also a transition I50 m 'non-linear' to 'linear' behaviour of the dielectric response can be observed in some cases above a certain voltage.

Statistical analysis of diagnostic indicators during an accelerated ageing experiment for XLPE cable specimens

“…Various studies have been performed which show some correlation with frequency domain dielectric response and water tree degradation [4][5][6][7]. Of particular interest is the behaviour of the loss with respect to frequency and at varying voltage levels.…”

“…Using these estimated linear constants (regression constants), the estimated values of y can be calculated by: Xb y  ( 7 ) With the "hat" symbol signifying estimated. The estimate of the errors ε can then be calculated by: y -y e ( 8 ) Where e are called residuals errors.…”

Condition assessment of XLPE insulated cables based on polarization/depolarization current method

“…When multiple polarization mechanisms exist in the cable, the polarization process can be modeled by a parallel circuit of branches which contain a series connection of resistor and capacitor according to the extended Debye model [35]. The equivalent circuit of the cable insulation is shown in Figure 9.…”

“…The three-branch model is used for simulating the internal polarization processes [35]. There are seven unknown parameters in the equation altogether.…”

Power Cable Structure Recovery and Application Based on Mould Melt Joint

“…The technical staff is professional full-time production technician, and must undergo a rigorous training of MMJ. The MMJ production environment is the same with the traditional cable accessories installation, no special requirements [4]. A key part needs a clean environment, the professional and technical personnel use the supporting the positive carry-conditioned clean studio, anti-static clean clothes, pollution dedicated hood, gloves, anti-pollution devices and tooling to control the process and ensure a clean environment.…”