HVDC Overhead Line Corona Characteristics: A Modern Toolbox and Geographic Specificities

Abstract

The energy transition that needs to happen in the face of the climate crisis requires electric transmission grids to have a higher capacity to absorb power flows. An important technical limitation in this regard are corona effects around overhead lines. This thesis presents tools and methods to assess the long-term corona characteristics of HVDC overhead line corona. Advances in material sciences allow to study the fundamental interactions of water droplets in electric fields on different surfaces. These interactions and the way they can lead to partial discharges are explained using experimental results as well as predictive simulations models and metrics are given to characterize the corona performance of surfaces. Based on modern IoT technologies, a unified sensor platform is presented that can measure different heterogeneous corona quantities while being efficient in terms of both energy and cost. The platform's capabilities and usefulness are demonstrated with experiments on test lines. Novel visualization techniques for partial discharge measurements are introduced as well. These methods are all required to enable meaningful long-term measurement of overhead line corona. Long-term results of an outdoor HVDC test line in the Swiss urban environment are presented. On their basis, trends are identified while still showing the variability in long-term corona data. It is discussed to what extent corona effects are specific to climates and environments and what the important metrics are in this respect. The unified IoT sensor platform is specifically introduced to make it easier to deploy a large quantity of corona measurement devices and thus monitor corona performance of overhead lines over entire territories traversed by transmission lines.