Study of electric field distribution in the high voltage stator bar insulation in presence of different shapes, locations and sizes of cavities

Abstract

The insulation system represents one of the most critical elements in any high voltage equipment, inclusive of any cabling and machineries. 60% of the faults and errors occurred in the insulation system are due to partial discharge occurrence which damage the high voltage machines and equipment, leading to an incurrence of huge expenses to replace them. The focus of this research is on the electric field distribution inside stator bar insulation system machine related to partial discharge phenomena. This research is manifested through the study of high voltage stator bar insulation’s electric field and potential distribution, coupled with follow up investigations into the ramifications of cavities of different distinctive shapes and the impact of the different positioning and sizes of cavities on the insulation system. The Finite element method (FEM) is the method that will be utilized in analyzing such simulation of the high voltage stator bar with the COMSOL software. A 2D modelling of stator bar insulation is conducted for this research to enhance an advanced understanding into the response of electric field distribution corresponding to distinctive shapes, positions and sizes of cavities within the insulation of high voltage stator bar. This outcome of this research will contribute majorly to the electrical power industry through acknowledging the presence of cavities and high electric field distribution relational to partial discharge activities while minimizing or preventing any faulty breakdown in stator bar machine that causes costly power failure in generation, distribution and transmission of electricity. The results from this research shows that the shapes, locations and sizes of cavities have a major influence on the electric field distribution inside the stator bar insulation whereby the presence of ellipsoidal shapes cavities give rise of electric field intensity twice the original (when no cavity is present), followed by the unknown shapes cavities which contributes 72.31% increment and spherical cavity which brings about 54% rise in the electric field strength. In terms of locations of cavities, the nearer the cavities located to the conductor region (at the inner insulation surface) as well as the edgy parts of the geometry, the higher the electric field is established inside the cavities. Apart from that, as the sizes of cavities increases from 0.22mm to 1.10mm, the electric field stresses inside spherical, ellipsoidal and unknown cavities sustain a drop of 19.08%, 12.09% and 28.57% respectively. This result deduces that highest inhomogeneous electric field stress is detected inside unknown shape cavity which increases the risk of electrical breakdown in this shape of cavity.The insulation system represents one of the most critical elements in any high voltage equipment, inclusive of any cabling and machineries. 60% of the faults and errors occurred in the insulation system are due to partial discharge occurrence which damage the high voltage machines and equipment, leading to an incurrence of huge expenses to replace them. The focus of this research is on the electric field distribution inside stator bar insulation system machine related to partial discharge phenomena. This research is manifested through the study of high voltage stator bar insulation’s electric field and potential distribution, coupled with follow up investigations into the ramifications of cavities of different distinctive shapes and the impact of the different positioning and sizes of cavities on the insulation system. The Finite element method (FEM) is the method that will be utilized in analyzing such simulation of the high voltage stator bar with the COMSOL software. A 2D modelling of stator bar insula...