Diesel Generator Response and Coal Fire Response

Dear Gents,

We have 12 diesels generator @4 MW which set isoch mode on the governor and paralell with 2 coal fire plant @65 MW which set droop via transmission line. When the "giant load" switch on or switch off, both DG and Coal fire plant maintain the frequency back to stable i.e 60HZ, of course initiate by the DG plant as isoch mode of governor.

The processing both DG plant and Coal fire plant back to ideal frenquency (60Hz), they need to take time a few mili second until second. My question is:

1. How do we can determine the diesel generator and Coal fire plant were in fast response or slow response. How do we calculate whereas we have the historical data:MW load, frequency drop when "the giant load" switched on (starting)

Your kindly help is highly appreciated