Gas turbine control system

A gas turbine control system for controlling a gas turbine unit including an air compressor for producing compressed air, said compressor having inlet guide vanes or blades for adjusting an air flow rate into the compressor, a combustor for combusting a fuel mixed with the compressed air from the compressor to produce a combustion gas, a gas turbine receiving the combustion gas from the combustor and driven by the combustion gas to drive the compressor;

• and an electric generator connected to an electric power system:
• said gas turbine control system comprising:
• an inlet guide blade control mechanism configured to control the inlet guide vanes or blades to change air flow rate into the compressor;
• a fuel control valve provided to change flow rate of the fuel into the combustor;
• a speed-load control mechanism including a speed control mechanism and a load control mechanism, said speed-load control configured to operate on said fuel control valve to control the flow rate of the fuel so that the gas turbine has a rotational speed coinciding with a set speed value;
• a combustion gas temperature control mechanism that controls the flow rate of the fuel so that the combustion gas temperature does not exceed a set temperature value;
• a system frequency abnormality sensor that operates to detect such a variation of frequency of the electric power system as to cause the power system to go out of normal operation;
• and
• said combustion gas temperature control mechanism having a disabling mechanism responsive to operation of said system frequency abnormality sensor to make the combustion gas temperature control mechanism inoperative to thereby have said fuel control valve controlled by the speed-load control mechanism, to restore a system frequency.