Madison Gas and Electric determined Tuesday the cause of the Monday-evening blackout that left most of the State Street and Langdon Street areas powerless.
Bryan Brosamle, MG&E Manager of Corporate Communications, said authorities intentionally shut off the power to combat a small fire caused by the insulation encasing underground cables.
\What happens when cable overheats is the insulation starts to burn and needs to be replaced,"" Brosamle said. ""So that's what we were doing all day today.""
Brosamle said crews pulled old cable and the faulty insulation from the ground for most of the day yesterday and replaced it with new cable.
MG&E CEO Gary Wolter told Ald. Mike Verveer, District 4, the initial problem occurred at the MG&E substation on North Murray Street and traveled underground through the utility work to the eventual problem spots. Wolter also told Verveer there were ""problems"" with a contractor working at the substation who was hired by UW-Madison.
The faulty cable overheated in two locations-the intersection at West Johnson and State Streets, and the intersection of Langdon and Henry Streets.
Brosamle added there was more than just smoke emanating from underground.
""When manhole covers come off, oxygen gets into the manholes and flames come out and that sort of thing,"" Brosamle said.
Authorities intentionally shut off power to prevent the spread of the fire and provide safe working conditions for MG&E workers. Brosamle explained when the power of the cables is off, the source of the heat gradually recedes, the cable cools and at that point, the insulation will stop burning and the fire will extinguish itself.
Brosamle said crews are continuing to do follow up work to make sure the damaged sections are repaired to prevent further similar incidents.
""The system is back in operation and some of the damaged cable was repaired today,"" he said.
""The CEO pledged to me that they were working very hard to check all of their assets in the downtown area,"" Verveer said, ""so a repeat of Monday's occurrence would never happen again.\
