Who knows, maybe impotence too.
Seriously. There is a well-established link between stray current from high-voltage lines of the kind that feed light rail systems and the accelerated corrosion of underground pipes.
Houston, for example, first identified leakage from its light rail line back in 2005. That system, like Charlotte’s South Blvd. line, also uses Siemens light rail cars. Stray current issues have also been reported in connection with light rail systems in San Francisco, Seattle, Denver, and Salt Lake City. In May, a Houston hospital sued the local transit authority over repeated current leakage issues.
CMUD and the city of Charlotte should be checking for stray volts around the current spate of leaks. Certainly the leak that sprang up yesterday along South Blvd. merits a closer look for any connection to the near-by light rail line and stop.
Update: CATS’ Siemens S70 cars are DC powered, 1500-volts. Here’s why this matters from a 2006 article in Pipeline & Gas Journal:
Substations with DC (direct-current) rectifiers supply electricity to the train through an overhead cable via a trolley or a pantograph. DC power is preferred for rail transit because of its superior torque characteristics. The overhead cable is connected to the positive side of the rectifier. The rails on which the train travels serve as the negative (return) conductors connected to the negative side of the rectifier.
The DC current will use any conductive medium to return to the substation. This means the entire LRT system, including trackwork, power system and other equipment, including train yards, shops, etc., can potentially send stray electric currents, sometimes called “leakage currents”–i.e., unwanted, non-designed currents–into the surrounding soil and onto nearby buried structures. Stray-current corrosion occurs at the point where the current leaves the pipeline, carrying iron ions that became positively charged when they lose one or more electrons.
And it does not take long for this process to cause damage. The article notes that it only requires a one-ampere current discharging continuously from a steel pipeline to remove “approximately 20 pounds of steel in a year.” Houston’s MetroRail began to have issues with discharge only one year after it started service.
One key question is the extent to which pipes and other utility lines, which we pointed out back in 05 are packed in old railway right-of-way of the kind CATS re-used for the South line, were moved in order to insulate them from any stray DC current in the ground. The next element is a robust cathodic protection system and a regular testing regime of its effectiveness.
Did CATS, the city, CMUD, Duke Power, Piedmont Gas and everyone else get together to hash out this issue? And what is the status of the current testing regime?
Update II: A 2002 audit by King County (Seattle) found insufficient cathodic protections for parts of its light rail infrastructure which required repairs.
