System for supplying fuel to gas turbine combustor and method for supplying fuel to gas turbine combustor

The purposes of the invention are to reduce the consumption of high-calorie gases such as a coke oven gas (COG) during the running of a gas turbine, and prevent the gas turbine from being shut down due to clogging of a pilot line or a trouble with a compressor for compressing the high-calorie gas, thereby providing improved reliability for the gas turbine. At the time of starting the operation of the gas turbine (11), a combustor (17) is supplied with high-calorie fuel and low-calorie fuel through both a first fuel supply system (31) and a second fuel supply system (32), the first fuel supply system supplying the high-calorie fuel to a first nozzle constituting the combustor (17), the second fuel supply system supplying the low-calorie fuel to a second nozzle constituting the combustor (17). When the gas turbine (11) has reached the output at which the gas turbine (11) can be continuously operated only on the low-calorie fuel, supplying the high-calorie fuel to the combustor (17) is stopped so that only the l