Reverse Power Protection for Gas Turbine Generator

[zaboli]

Hi All. What is the reason for using 2 Stage protection for reverse power for gas turbine generator (21MW)? How to calculate these 2 settings?
Thanks for your help.

 

[crshears]

From my limited experience, the lower reverse power setting would come into play in at least these two scenarios: [a] when all fuel supply to the unit is lost [therefore no further combustion] or say, during an over-frequency trip, where the main output breaker remains closed, with the unit synchronized to the system and motoring. The load drawn in this scenario is considerable, it being the compressor's normal power consumption at speed plus the windage losses of the turbine.

The lower reverse power trip setting would thus be 75-80% of this load, with no intentional time delay built in. Since most GTG designs I know of will not be damaged by brief periods of motoring, this setup is more than adequate for this situation.

The higher reverse power setting would be a backup protection to the split-phase, over-current, or other alternator protections; I will let other address what the trip setting for this should be.

CR

"As iron sharpens iron, so one person sharpens another." [Proverbs 27:17, NIV]