CEM engineer Dr. Xianyong Feng presented a paper describing a novel way to identify and locate electrical faults in dc circuits at the 13th IET International Conference on Developments on Power System Protection on March 7 – 10, 2016 in Edinburgh, Scotland. The research combined theoretical analysis with hardware-in-the-loop testing to validate the value of the approach. The research was conducted in collaboration with researchers at ABB’s Corporate Research Center in Raleigh, NC.
For more than a century ac circuits have dominated power systems, the outcome of a significant struggle between Thomas Edison, a proponent of dc power, and George Westinghouse, the face of those supporting ac. The fight became sufficiently nasty that Edison suggested dubbing prisoners executed in electric chairs as “westinghoused”.
One of the reasons ac became dominant was that it was easy to build a fuse, or the modern technology of a circuit breaker, to stop the flow of current. An ac current reverses itself 60 times a second, thus naturally extinguishes any arcs that might form. By contrast, dc current is constant, so if a fuse blows or a circuit breaker opens, an arc typically forms and the current persists, which can pose a safety hazard without taking proper protective measures.
CEM’s High Bay facility accommodates larger power electronics assembly and testing. In addition, it houses two dedicated EMI/RFI shielded control rooms to isolate instrumentation and controls during high energy testing. Fast transient data can be collected using digital storage oscilloscopes and custom designed data acquisition systems are available to monitor and analyze the performance of rotating electrical machines, including rotor vibration and housing accelerations in both time and frequency domains.
However, today technologies are much different than they were a century ago. Increasingly, off-grid communities in developing countries are adopting solar powered systems supported by batteries, both which operate at dc. In addition, rooftop solar systems are growing in popularity in the US. Since electronics generally operate more efficiently at dc, new research studies are emerging like one at the University of Texas in collaboration with the Japanese government agencies to assess the effectiveness of a dc powered high performance computing cluster in its research computing center. Finally, dc power is seen as an enabling technology for future military ships, providing a power dense solution needed for future versatility.
The growing importance leads to a growing need to dc fault protection. Dr. Feng’s research is a strong contribution to the ongoing work at CEM in dc power. This research includes two papers on dc microgrid considerations for off-grid communities, a paper showing the behavior of series faults in high power dc systems to help avoid fires in ship power systems, and continuing work on dc computer centers.
The key innovation in Dr. Feng’s work was to use changes in the circuit inductance to locate faults. This approach provides the opportunity for the rapid identification and location of the fault. Allowing for isolation without the delay associated with a hierarchical communication and control system.