How does the load of the Black start DG Set Varies with variation in grid frequency when DG Set is connected to grid for trial run.

The capacity of BSDG set is 3.5 MW if it is synchronised to grid at 2MW load for trial run to check the healthiness of the BSDG.
What will happen to its load with frequency variation in grid and How does the governing of DG Set takes place describe in detail about the governing.

 

The frequency (in Hz) of a synchronous AC electrical generator (or, alternator) is equal to the product of the number of poles of the generator times the speed of the shaft (in RPM), divided by 120: f = (p * N)/120.

Therefore, the speed of a synchronous AC electrical generator (and its prime mover--even if that prime mover is directly connected to the generator or if the prime mover is connected via a reduction gear) is equal to the product of the frequency of the AC generator times 120, divided by the number of poles of the generator: N = (120 * f )/p.

Any synchronous AC electrical generator (regardless of the prime mover being used provide torque to the generator) connected to an AC electrical grid in parallel with other generators will have its frequency/speed controlled by the electrical frequency of the grid. (The exception: a generator with a prime mover configured to operate in Isochronous speed control mode.)

What will happen to the power output of your diesel gen-set with variations in grid frequency depends on how the governor is configured and operated. For example, is the governor configured to operate in proportional load control or Droop speed control when it is connected to other generators on an AC electrical grid?

Consult the diesel's governor instructions for details of how your diesel gen-set is controlled. There are usually simplified block diagrams provided in the instructions for an overview of how the governor can be configured to operate.

But, one thing is certain: the frequency of the generator--and the speed of the diesel--will fluctuate with variations in grid frequency.

The concepts of speed regulation, or Droop speed control, and Isochronous speed control apply to virtually any prime mover/generator combo. The implementation varies with the governor manufacturer, but the concepts still apply. As electronic governors have replaced mechanical- or hydraulic- or electro-hydraulic governors, the methods for controlling power output of AC electrical generators operated in parallel with other AC electrical generators on an AC electrical grid have changed. With the ability to include power output (load) in the governor control loop, the designers of governors have different options than those of fifty- or one hundred years ago.

But, gover designers/manufacturers still have to build governors which can: control frequency (Isochronous) and/or share load with other generators and their prime movers when connected to an AC electrical grid (some sort of proportional control, either Droop speed control or proportional load control).

 

at site we had a problem with black start DG set when it started on auto due to power failure but its 11KV braker tripped with indication over frequency, is it possible in this condition when BSDG operates for restoration of spplis in isolated mode.