Power Engineering

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Browsing Power Engineering by Subject "Basic insulation level (BIL)"

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    Displaced neutral on woodpole structures with 300 kv basic insulation level rating (BIL)
    (Vaal University of Technology, 2022-03-06) Becker, Taryn Robin; Britten, A. C., Prof.; Walker, J. J., Prof.
    The influence that the geometry of the woodpole structure has on the voltage developed across the 500 mm basic insulation level (BIL) coordination gap and conductive bonding accessories is discussed in this dissertation to further understand possible reasons for failures of woodpole structures as experienced in the field. A scaled woodpole structure comprising of porcelain insulators was erected under laboratory conditions to assess the relationship between the voltage developed across the 500 mm insulation coordination gap under balanced and unbalanced system conditions. Other parameters including the leakage current behaviour as well as the phase relationship between the under these conditions were also investigated. The laboratory scaled structure was energised using three single phase 132 kV voltage transformers. Furthermore, a two-dimensional model was developed to simulate the electric field condition in and around the phase insulators and the coordination gap using QuickfieldTM, a finite element (FEM) simulation software. The experimental, as well as the simulation results, showed that the configuration of the insulators has an influence on the voltage developed across the coordination gap. The two structures with different insulator configurations were considered with porcelain insulators. The difference between these configurations was the installation of the insulators, for configuration 1 all the insulators were erected in the vertical upright position whereas for configuration 2 the outer two insulators were inverted downwards in the strain position. The magnitude of the BIL voltage developed across the gap was the highest for configuration 2 under balanced conditions in comparison to configuration 1 when all the insulators are upright, this condition is true for both the laboratory model and well as the simulation model. Certain scenarios were used to compare the scaled woopole model and the 2D FEM model. The parameters such as voltage, leakage current and phase relationship under balanced and unbalanced conditions were considered. Based on the more common network faults such L-L fault, L-G fault, L-L-G and L-L-L-G faults, the approach looks at a more specific fault and the impact this fault has on the deterioration of the wooden structure. The emphasis is on what occurs in the field when a phase is disconnected from its insulator or when more than phase is disconnected from the structure. Included in the analysis, is the influence of the insulator geometry and its role. Findings from the laboratory structure and FEM model indicated that the worse-case condition was for configuration 2, when phase B is disconnected from structure. When two phases were disconnected, results from the FEM model indicated that configuration 1 was worse-case compared to that of the laboratory structure have higher values measured on configuration 2 when only phase A is connected to the structure.