Electric Field Modeling in Cable Terminals with Defects and Fed by Power Converters

Due to the increase in the amount of renewable energy sources incorporated into the distribution network, there has also been an increase in the usage of electronic power converters. The non-sinusoidal voltage waveforms from these converters have been identified as the cause of problems in the insulation systems of some electrical network elements. This is a problem that must be dealt with to ensure that incorporating renewable energy sources into the network does not affect its reliability. In this work, an analysis of the dielectric stress in medium voltage cable terminals with refractive stress control layer and fed power converters is carried out. The calculations are made considering terminals with and without defects during their installation. Due to the need for three-dimensional geometries to model cable terminals with defects and time-stepped simulations to evaluate the non-sinusoidal waveforms from the converters, possible techniques to reduce computational burden are analyzed. The results show that defects considerably increase the maximum electric field and the time average volumetric loss density in the stress control material. It is also observed that although a three-level pulse width modulated waveform increases the electric field and loss in the stress control material, it is well below the levels due to defects. The combination of installation defects in terminals and voltages from converters generates a condition with an elevated risk of failure.