High steam temperature occurred during cold start of the ultra supercritical 660MW unit in Jiangsu Guohua Chenjiagang Power Generation Company which was with tiny-oil ignition.On the basis of reason analysis

the countermeasures were proposed

namely putting the heater into service at the beginning of the unit start-up to enhance the feedwater temperature and control the steam temperature

which avoided the situation that the turbine was difficult to load up due to the excessive metal thermal stress after the unit was connected to the grid.By on-line monitoring and adjusting the superheat degree of the steam at inlet and outlet of the economizer

the over high thermal deviation on the water wall was prevented

and the start-up safety of the unit was ensured.