On Thursday, the agency's fisheries and ecology team isolated a 100m area of the river next to Ravensbury Park in Merton and used equipment which generated low voltage electric currents to check how many fish survived.

BBC: NEWS | UK | England | London | Toxic spill in river kills fish

New York City, electric power is transmitted by high voltage cables encased in steel pipelines to electric substations where the power is converted to low voltage feeders supplying about 55 distribution networks.

FORBES: Brave New World For Big Apple's Power Grid