I & C of a power plant is a broad subject that includes online operation of various control loop strategy,start-stop of equipment and start up,shut down process as well as safety interlocks.
The basic objectives of a control is to operate the thermal power station successfully,economically,safely ,reliably and continuously.

Efficient operation of power plant - The objective is to maintain the availability or up-time of the plant system.to maintain the parallel running boiler up-gradation so as to achieve the assure steam availability as well as coal consumption ratio.
modern controls are more reliable and can be readily adjust to load swings caused by varying total plant operation.so a continuous supply of steam at the desired condition of pressure and temperature required.

Economic operation - Low cost operation of boiler require following steps...
1.excess air optimization control  2. increase the thermal efficiency of boiler 3. reduce process upsets 4. minimize steam consumption per unit of power generation in the turbine 5. minimize blow down 6. optimization of boiler operation by proper load sharing between parallel boilers 7. proper maintenance schedule- AMC,TBM,CBM,PM,Kaizen etc.  8. Readily make data availability for remort monitoring to determine process unit optimization,load allocation and efficiency of boiler.

Safe operation of power plant - 1. safety to men 2. safety to equipment's 3. flame safety-burner management system(already data provided in my earlier posts) 4. safety analysis(diagnosis,alarm etc) to boiler and turbine 5. Fire management system etc

Pollution control in power plant - controlling the following can provide a pollution free environment in power plant
1.oxygen percentage 2.Fuel flow 3. ash disposal 4. more plantation 5. SPM 6. SOx-Nox 6.Stack temperature control etc.