Ameren has restarted Missouri's sole nuclear plant after investigating a fire in electrical equipment that led to an automatic shutdown last month.The Westinghouse pressurized water reactor was running at 65 percent power Monday, according to the Nuclear Regulatory Commission. In a release, Ameren concluded that an electrical fault in the main power cables exiting the plant led to the outage. Arcing resulted when a dislodged ventilation louver came in close proximity to the electrical cables, according to Ameren. The damage did not require major equipment replacement.The plant had declared an unusual event July 26 after workers reported indications of a fire, according to an NRC event report. Smoke from burning electrical insulation and melted ductwork briefly prevented access to that part of the turbine building, the NRC reported, although the arc was more than 50 feet from any safety-related equipment. A resultant turbine trip caused the reactor to shut down automatically from full power.