Alternators and Load Sharing

Better questions will yield better answers. Please explain what you want.

Alternator load will be depends on the fuel input of the prime mover. when the fuel is more than the other alternetor set, this Alt. will take more load, i.e KW. if the fuel is less, it will less load

KVAr sharing depends on the excitation current of the aletrnator. If the Exc. current is more the alternator will carry more current and the more KVAr than the other alternator, if the Exc. current is less, the KVAR will be less.

Auto load sharing relays will monitor the KW and KVAr levels and give the signal to the governor of the prime mover and the AVR of the alternator accordingly.

Dear Friend,

Your question is not clear. What you want to ask should be clearly spelt out.

What I infer from your posting is that – you are operating alternators in parallel and you want to about load sharing by the alternators after synchronization. If it is so:

The droop character of the Alternator will dictate on the load sharing and it is not any linear mathematics calculation or proportional sharing will not occur.

You should know the droop character of each alternator i.e., the voltage drop from No-Load to Full load in relation (while working independently) to the frequency is to plotted on a graph.

I am not able to paste a model graph. Plot the frequency in the vertical axis and the voltage drop in the horizontal axis. After synchronization the alternator will have common frequency only. The slope of droop character line will have lesser slope for the alternator having lesser voltage drop and the slope will be steep for the alternator having larger voltage drop.

Normally the Droop will be in the range of 4% to 6% say for a frequency range of 50 t0 48 Hz.

While you synchronize the alternators are working and supplying power to the total connected load, the alternator having lesser voltage drop from No-Load to Full-Load will share more load for a given frequency. If you plot the graph, you can precisely calculate the load sharing pattern.

Same philosophy will apply for the prime mover(s) of the alternators where the droop character will apply for the speed from No-Load to full-load.

DHAYANANDHAN.S

If OP is asking about load sharing, there are several industry standard controllers:

Woodward, Deep Sea, and more