A diesel power plant, consist of 3 generator sets, each installed capacity is 3.1 MW,. 8pf,50hz,actual capacity of each generator now is 2.5 MW, due to running hours and maintenance.
11KV feeder come from the substation to the bus bar of the diesel plant, where the diesel generator sets parallel with, in order to improve voltage, since the 220KV come along a distance of nearly 350 Km, and there is voltage drop.

SSome times the power factor of one generator becomes more leading or capacitive and there is no way to readjust it so as to become. 8 lagg or near, we put it's breaker off before it becomes more capacitive and problems occur.
What are the reasons and how to correct.

 

Play with your excitation. You need to slowly reduce the excitation - provided the equipment has those controls. Usually smaller machines may not have such user adjustable controls.

 

Thanks swami good answer.
Consider that I am working with one generator to feed this capacitive load, and I am not connected to grid, in this mode of operation the out put of my generator (I. e active+reactive) must be greater than or equal to load demand, other wise I must parallel one or two of the remaining generators to face requirements of load demand.
Now if I am parralled to grid with only one generator, and I saw that capacitive load, here I must decrease excitation, OK some times three is good response and pf from. 95 leading will slowly move towards unity then to lagging direction, but some times pf will not change due to decreasing of excitation currentit will stand. 95 or. 9 leading, so we are forced to trip the gen. C. B to avoid greater problems, is there something else we can do in situation like this?

 

When a generator operates at low active power (real power) output relative to its reactive power capability, it may absorb reactive power, causing a leading PF. This is more likely when load demand fluctuates or decreases significantly. Devices like series capacitors or voltage regulators can minimize voltage drops along the 350 km line, reducing the burden on the diesel plant for voltage correction.

 

Play with your excitation. You need to slowly reduce the excitation - provided the equipment has those controls. Usually smaller machines may not have such user adjustable controls.

I mentioned in my reply to you below :
Now if I am parralled to grid with only one generator, and I saw that capacitive load, here I must decrease excitation
This is by mistake forgive as excitation must be increased to over come the reactive leading current in gen. Stator

 

When a generator operates at low active power (real power) output relative to its reactive power capability, it may absorb reactive power, causing a leading PF. This is more likely when load demand fluctuates or decreases significantly. Devices like series capacitors or voltage regulators can minimize voltage drops along the 350 km line, reducing the burden on the diesel plant for voltage correction.

As far as I know the minimum distance for transmission line is about 200km, more than that you will suffer voltage drop at the receiving end.....

 

When a generator operates at low active power (real power) output relative to its reactive power capability, it may absorb reactive power, causing a leading PF. This is more likely when load demand fluctuates or decreases significantly. Devices like series capacitors or voltage regulators can minimize voltage drops along the 350 km line, reducing the burden on the diesel plant for voltage correction.

And this what was
done...
I. e the diesel power station I mentioned is at the recevieng end of the transmission line which comes from a distance of about 350KM,and the voltage regulator of this diesel p. P is used to improve the decreasing voltage of the transmission line when it's stepped down to the distribution voltage I. e 11kv