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Detection, characterization and extinction of electric arcs in DC Systems

Advancements in power electronics has sparked the adaptability of dc systems in varied application fields. The phenomenon of electric arcing in such dc systems, arising due to the absence of zero crossing of current during normal operation, has impeded the widespread proliferation of dc-based technologies in the market. Considering the advantages presented by adopting dc over the ac systems in terms of efficiency and compatibility with renewable energy, it is of great interest to remove any such impediments involved in developing a mature, viable and sophisticated dc system. In context of low voltage dc microgrids, a novel arc detection method has been proposed and validated through simulations as well as real time experiments. It is shown that the detection scheme is able to rapidly and selectively identify series arcing by solely monitoring the load side voltage. The boundaries associated with threshold trigger voltage selection and detection time are defined based on varied circuit configurations. The algorithm is designed to be tolerant to the grid side voltage fluctuations in order to avoid spurious triggering. In context of arc characterization in high voltage dc systems, the bus transfer facilitated by GIS disconnector is studied. Analytical expression for recovery and re-strike voltage is derived to enable their estimation from the measurable space variables of the experimental set-up. The simulation model emulating the experimental set-up and the parameter estimation methodology is developed and validated. By varying the configurable parameters like initial capacitor voltage, switching frequency and source inductances, the possible recovery voltages across the disconnector is simulated. Based on this, a series of experiments aimed at studying the arcing characteristics during bus transfer process are designed and conducted. Finally, analysis tools are created to estimate the parameters describing the arc behavior, such as burn time, starting arc current, corrected arc voltage, input arc energy, recovery and re-strike voltage.