To install black start generator for 2 power generators 45 MW

[SA07]

Hi
We have 2 turbo alternators 45 MW 11 kV 50 Hz each exporting to the utility grid. We intend to install a stand by generator to do black start of a turbo alternator in case of total black out of the national grid and then export some MW on the grid.

The auxiliary consumption of one plant before synchronising is about 2 MW.

We have a series of 11 kV circuit breakers next to each other for each unit and a common busbar as shown in the attached doc. After each unit are synchronised with the network, we want the std by generator to export some power to the grid.

Our biggest single motor is the boiler feed pump of 1 MW.

What rating of std by generator do we need? Will a 5 MW be enough?

Then after synchronising both units, will we be able to export an additional of 5 MW on the grid?
Is there a 5MW 11 kV std by generator on the market?
There is a request from the national grid company to increase our production because of some issues on the grid.

 

[RRaghunath]

For a DG set to have black start capability, its auxiliaries should be minimum and / or should be able to start on DC battery.
I am afraid 5MW could be large to be able to start on its own. You may discuss this with a reputed manufacturer before making a decision.
Since the black start power requirement is 2MW only, a 2.5 or 3MW set could be good enough. To cater to the starting power requirement of BFP, the generator alone can be of higher MVA rating. This is because 1MW motor may take 5MVA power during start @ a power factor of 0.2 (say). This is to say a DG set comprising 3MW Diesel Engine and 5MVA Generator.
Optionally, if a Soft starter can be added to the 1MW motor, the starting current can be limited to 2x the rated current.