Executive Summary : | The increase in power transfer and improvement in the efficiency of power delivery led to the design of UHV and EHV transmission lines as the electrical power consumption is expected to double by 2050. High voltage insulators play an indispensable role in maintaining the reliability of the transmission lines. Due to materials enhancement and development, Polymeric or non-ceramic materials are used in transmission line insulators. Electrical field along polymeric insulators is a function of various parameters such as voltage, insulator design, tower configuration, phase spacing , corona ring and design etc. Corona discharge has become an important factor not only because of corona losses but also due to electromagnetic interferences, degradation of the insulating material and flashover. External metal rings known as corona rings and grading rings are used to minimize the high electric field thereby mitigating corona discharge. Control of Electric field plays a crucial role in the service operation of polymeric insulators as the increased electric field distribution generates corona discharge and leads to breakdown. It may be controlled by proper design of insulator, corona and grading rings. The dimensions and location of the rings have a significant influence on the Electric field distribution. Hence optimum dimensions and location of the rings are indispensable and to be determined to ensure the longest dry arcing distance possible without reducing the basic insulation level. Electric field along the surface of creepage distance (triple junction) is considered as the most crucial area for the design of polymeric insulators. As the design criteria of polymeric insulator varies depending on mechanical and electrical stress, detailed analysis has to be carried out for the design of corona and grading rings (Diameter of the tube, Radius, type and number of the rings etc) for different types of polymeric insulators. The type and number of rings depends on tower, insulator set/string configuration, voltage class, etc. The relationship between the Electric field and the structural parameters of the ring is to be modeled using Artificial Neural Network (ANN) and optimized using various optimized techniques such as PSO, GA etc. All the above analysis are to be done for all EHV voltage classes starting from 33kV to 1200 kV. |