In the electrical room of a household waste incineration plant (HWIP), an external company was connecting a new supply cabinet for the electrical heat tracing of the fire protection system. At 3.38 pm, a general power cut affected the HWIP. A detonation was heard on the inverter of the instrumentation and control system. The maintenance department manually started up the generator which was locked out during the work. As it was not operational, the control room remained in the dark and the instrumentation and control system was inoperative. On-call staff were contacted. To prevent the fire from spreading to other installations, the staff activated a fire hose over the 2 waste loading hoppers. To limit the deformation of the boiler by the heat, it was supplied with water by manually opening the demineralised water valve to its maximum extent. The maintenance department shunted the faulty inverter 20 minutes later and got the servers and control station back into operation. At around 4:15 pm, an emergency shutdown of the installations was performed and the hydraulic systems and exhaust fan were turned on. Despite the fire-fighters’ actions, the combustion of waste spread along the supply ducts. The destruction of a thyristor in the inverter appeared to have caused the event. Several protective measures were implemented: cleaning of the grates, crates and heaters, repair of the ducts seals, replacement of the temperature sensors, circuit breakers and inverter, automated monitoring systems brought back into operation, and hydraulic testing of both lines, etc. After taking these measures into account, the 2 lines were brought back into service (after 12 days for line 1 and 8 days for line 2) in order to empty the storage pit of waste. Other preventive and corrective actions have been scheduled: study of separate supplies for hydraulic controls, doubling of the inverter, direct and independent supply for the inverters, and modification of the procedures while work is being performed (no work if both lines are in operation). Heat had deformed the ducts. Spraying the fire had damaged the refractory protection of the combustion chamber’s walls. The smoke treatment system had prevented any atmospheric pollution. The cost of repairing the installations has been estimated at €331,000 excluding taxes.