We have GE frame 6 Gas Turbine (30 MW) initially operating/controlled by Speedtronic Mark-IV control system and later on upgraded to Mark VIe. Generally we operate GT on part load (Preselected mode) as per our steam and power balance. Since last few days we have noticed continuous load variation from 16.5 to 19.1 MW (Machine set on 18 MW preselected load). TNR value is changing continuously though there is less variation in TNH value.