Our gas turbine is a GE MS5001, with MKV speedtronic control system.
Whenever the unit is running on FSNL and with load less than 1MW (NOT ON GRID), unit starts showing "manual shutdown." However, when it is fully loaded, like 20MW and is synchronize with the grid, unit does not show "manual shutdown."

Note, there is no alarm indication before showing manual shutdown.
What signal could have caused it?

 

There is something amiss with the Enumerated Data file and/or display configuration for the Status Field messages. Without being able to see the CSP (Control Sequence Program), the ENUMDATA.DAT file and the display file(s) it's really impossible to say what exactly is the problem and how to fix it.