INSULATED CONDUCTOR TEMPERATURE LIMITED HEATER FOR SUBSURFACE HEATING COUPLED IN A THREE-PHASE WYE CONFIGURATION

A heating system for a subsurface formation is described. The heating system includes a first heater (212) , a second heater (212) , and a third heater (212) placed in an opening in the subsurface formation. Each heater includes an electrical conductor (218) , an insulation layer (220) at least partially surrounding the electrical conductor, and an electrically conductive sheath (222) at least partially surrounding the insulation layer. The electrical conductor is electrically coupled to the sheath at a lower end portion of the heater. The lower end portion is the portion of the heater distal from a surface of the opening. The first heater, the second heater, and the third heater are electrically coupled at the lower end portions of the heaters. The first heater, the second heater, and the third heater are electrically coupled in a three-phase wye configuration.