AC vs. DC Hazards: Knowing the Difference Could Save Your Life

摘要

YOU MAY NOT REALIZE IT OR MAY never have given it a second thought, but if you live in a large metropolitan area, alternating current (AC) and direct current (DC) energy systems are all around you. Although I have studied these two systems for years, I didn't always know about it. I was caught completely unaware and surrounded by an invisible, lethal hazard. This is my near miss story and the lessons learned. In the summer of 2011, Seattle (WA) Fire Department Engine Company 25 responded to a report of "wires down" at Broadway and Madison Street, a busy intersection in Seattle's Capitol Hill neighborhood. It is a wide multilane intersection of five streets with electrical catenary wires for streetcars and electric buses traveling north/south and east/west. More than a thousand pounds of steel wire and hardware keep the system suspended under tension and deliver the current to the electric buses and streetcars through this intersection (photo 1, 2).