There is significant amount of investments from the provincial government to promote renewable energy based distributed generation. Renewable sources have introduced a new challenge to the present electricity grid, both from power system component's insulation and operational point of view. Since renewable sources have a power converter based grid interface; therefore, they bring high frequency voltage distortions and high dv/dt stresses on the insulation system of various power system components, such as cable terminations and distribution transformers. Electric field analyis and aging experiments have been carried out on cable terminations and distribution transformer paper insulation samples.
Effects of power system harmonics on distribution transformer insulation performance
Floating feeder resonances are one of the new challenges being put forward by the renewable energy based distributed generation (DG) installations. Generally, the harmonic injection from DGs are within the Institute of Electrical and Electronic Engineers (IEEE) standard 519-1992 limits. Although the harmonics are within the IEEE limits, they are a potential threat to power equipment's insulation system integrity due to floating feeder resonances. In this study an electric field computation is carried out on a high voltage coil, and it has been found that electric field distribution is significantly different under distorted voltage waveforms which may lead to localized partial discharges. Furthermore, an aging experiment is also carried out on a field aged paper sample from a distribution transformer under clean and high distortion conditions, and it has been found that aging rate significantly increases under high frequency distortions.
Cable terminations analysis under fast rise time pulses
There is a potential presence of amplified harmonic components in the power network grid when the resonant frequencies align with the harmonic frequencies that are being injected by power electronic components of the distributed generation (DG). The threat of an unacceptable total harmonic distortion (THD) could significantly enhance the electrical stresses on the insulation system of the power system components including cable terminations. The overall aim of the project is to conduct the ageing analysis of the cable termination under distorted voltage waveform and evaluate the termination insulation quality. Diagnostic techniques such as partial discharge detection, surface potential distribution measurements, surface temperature monitoring, and loss factor measurements serves to analyze the termination insulation. Simulation using COMSOL Multiphysics 3.5 is conducted for verification of the experimental results.
