Maximum Utilization of On-Base Emergency Generation after Sustained Utility Outage

摘要

The focus of this research will take advantage of the excess emergency generation capacity typically seen at any Air Force base and use it to backfeed the local distribution system to maximize the load supplied for sustained power outages. The model developed was intended to represent all Air Force bases and includes 2 distribution substations, 7 feeders, and 39 dispersed emergency generators. The generators range in size from 7.5 kW to 2.5 MW and provide a total of 13.9 MVA of potential capacity. Four system states were simulated in this research. Power flow and short-circuit tests were performed for each state to verify and check solution feasibility. The base case modeled normal operating conditions with the utility supplying the entire load. The first scenario simulated the loss of utility so only critical loads were powered by their respective emergency generators. This created 39 electrical islands leaving an excess generating capacity of 8.23 MVA. The second scenario attempted to connect generators so power could be supplied to some noncritical loads. Through trial and error, while verifying feasibility, 22 electrical islands were created reducing the excess generating capacity to 4.07 MVA. The third scenario employed essential loading tactics to maximize the quantity of loads supplied. Here, 18 electrical islands were formed giving an excess generating capacity of 4.71 MVA. There are several issues that may prohibit connecting generators to an existing distribution system. Transformers will need to act as step-up transformers for the generators, and may have adverse effects on short-circuit currents and harmonics, depending on their size, impedance rating, and configuration. Unintentional islanding may damage equipment and cause harm to crews who maintain the system, and the coordination and existing protection scheme may become invalid as a result of adding distributed generators.