Efficient Corona Modeling for FDTD Simulations

The existing corona model for the Finite-difference time-domain (FDTD) method represents the gas ionization process as the radial expansion of a conductive region around the wire. Despite being a simplified representation of the phenomena involved, the model has a high computational cost by requiring the discretization of the area near the wire into small cells. Furthermore, no physical law is proposed for determining this region's conductivity, which may vary from application to application. Its evaluation against experimental results, in turn, requires running time-consuming simulations. In this article, a new methodology to represent corona in FDTD simulations is presented. The method is based on representing the variation in wire capacitance under corona by an equivalent radius, which is obtained from measured charge-voltage curves. This approach is simple to implement in the FDTD method and does not require grid refinement, allowing for fast simulations. The proposed method is validated with measurements of the charge-voltage curve and the current injected into a 44 m horizontal conductor. Results show good accuracy of the method, with mean absolute errors of 2.4% and 2.9% for negative and positive polarities, respectively, considering measured charge-voltage curves, and a 100 times reduction in computational time compared to existing model.