Application of new solid insulating materials and gases to future advanced gas insulated systems

摘要

Gas insulated equipment, such as gas insulated switchgear (GIS), gas circuit breaker, gas insulated line and gas-filled power transformers, has widely been applied to power equipment thanks to its high reliability and compactness. Improvement of SF_6 insulation system in the gas insulated equipment is, however, required for a further downsizing of the equipment with keeping high reliability for the purpose of saving the investment cost or reducing SF_6 usage, one of potent green house gases. This paper deals with new solid insulating materials and gases to realize future advanced gas insulated systems, introducing the following recent topics in Japan on the improvement of dielectric performance of the systems. (1) New gas composition using thin dielectric coatings for gas insulated system. - The influences of contaminated metallic particles in N_2/SF_6 gas mixtures insulated system are suppressed by an excellent thin dielectric coating, modified phthalate-ester on the enclosure inner surface. - Highly pressurized CO_2 gas insulated system up to 1.0 MPa can be improved by applying thin dielectric coated high-voltage (HV) conductors applying new coating material, TUFRAM. - A thin dielectric coating to HV conductors is also effective to improve the dielectric performance of high pressure dry-air at 0.5 MPa. (2) Practical thick dielectric coated electrode (TDLE) for advanced gas insulated system. - TDLE using new materials made of epoxy resin with appropriate fillers has two features: (a) reduction of the maximum electric field strength in electrode systems, (b) extremely high dielectric strength compared with bare electrodes. (3) State-of-the-art functionally graded materials (FGMs) for solid insulators in gas insulated system. - New insulator materials of grading of relative permittivity ε-FGM can reduce a local field concentration at triple junction where solid insulator meets metal electrode in gas insulated system and can also improve the life time of insulating spacers.