A Novel Self-Protected Resonant Capacitive Transformer with Power Harvesting Interfaces to Supply Overhead and Ground-Level Loads in High-Voltage Power Systems

Large-scale monitoring of the operation of transmission and distribution power grids has led to important changes in both the design and equipment. The replacement of conventional measuring systems with nonconventional measuring ones based on sensors for electrical and non-electrical quantities placed right on the overhead lines improves significantly the reliability of the power network. The paper describes a new power conversion system with two power taps that allows both the power supply for the sensors at high potential and the power supply for the sensors processing interface or other consumers on the ground. For this purpose, a resonant capacitive voltage transformer principle has been modified so as to be self-protected against overvoltages and to allow the stabilization of the output power regardless of the load. The frequency-domain analysis proves that these properties are obtained using a different tuning of the resonant circuit compared to the network frequency. The self-protection capability is the key point of our approach, which allows lower manufacturing and maintenance costs alongside a better reliability compared to the known resonant capacitive transformers tuned to the grid frequency. Such an apparatus with a nominal voltage of 123 kV is practically demonstrated in a novel, air insulated sustainable construction, with maintenance-free ceramic capacitors in a composite insulator.