Stretched grid finite difference method for computation of electric field in composite insulators with defects

Abstract A 2-dimensional stretched grid finite difference method for the calculation of electric field in composite insulators for up to 1000 kV is presented in this paper. This method is shown to be applicable for composite insulators with and without defects where the inherent axial symmetry cannot be used to simplify the modeling process. This method was initially used to evaluate healthy composite insulators of single and double strings with and without corona and grading rings. Further, a conducting defect was simulated at the high voltage electrode to evaluate 69 and 138 kV insulators. The electric field was also computed using a package based on boundary element method. The accuracy and computational time for all the cases were compared. It has been shown that the proposed method can yield fairly accurate results when compared to other methods, but in a significantly reduced time taken by the latter. The electric field computed for 69 kV composite insulator with defect was compared with the actual measurements using an electro-optic probe. The results show a good agreement. Stretched grid method promises to be an efficient way of quickly computing electric field and this paper quantifies the information obtained for insulators with wide range of system voltages.