# alternators connected to infinite bus bar

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#### lukesh

hi..

recently i'm learning about operation of alternators connected to infinite bus bar. i understand the effect of increase in excitation or turbine input on various parameters. But now i m facing a confusion regarding alternator connected to infinite bus bar.

i read that an infinite bus bar has constant voltage and frequency (speed) "regardless how much kw or kvars are supplied or drawn from it"

so how an operator in generating station knows that load has increased?

do increase (large) in load in any particular area effects all the alternators in infinite bus bar.

#### CSA

hi..

Multiple alternators <b>synchronized</b> to an infinite bus are all acting as one large alternator. No single alternator's output can have a different frequency than that of the infinite bus. This also means that, for all intents and purposes that the voltages of the alternators are also nearly identical--it would be very difficult for one alternator to raise the entire bus voltage.

We, are of course, speaking of normal operating conditions. Under adverse conditions, lots of unusual things can happen to an infinite bus to which multiple alternators are <b>synchronized</b>.

One of the conditions that can cause the frequency all of the alternators <b>synchronized</b> to an infinite bus to decrease is if suddenly a large alternator or group of alternators were disconnected from the infinite bus. There would be a lack of sufficient generation to supply the load <b>at the rated frequency.</b>

Conversely, if a large block of load(s) were to suddenly be disconnected from the infinite bus then the frequency of the infinite bus--and of all the alternators <b>synchronized</b> to the infinite bus--would increase because there is an excess of generation to supply the load <b> at rated frequency</b>.

Energy can't be stored on an infinite bus, so if there's too much generation (too much torque being provided to the alternators) for the load(s) then the speed will increase. If there's not enough torque to maintain rated frequency because there's too much load for the amount of torque being supplied to the alternators then the frequency will decrease.

Hopefully, soon, there will be inexpensive ways to store energy on an infinite bus. That will solve a lot of problems in many parts of the world.

Hope this helps!

By the way, there have been lots of threads on control.com which use a bicycle analogy to describe an infinite bus. Most of them deal with droop speed control, but the analogy would be applicable to your question.

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#### lukesh

> Multiple alternators <b>synchronized</b> to an infinite bus
> are all acting as one large alternator. No single alternator's output can have a
> different frequency......

thanks sir for beautiful explanation.

i tried to relate my problem with a mechanical system, and i found this:

i consider two gears of same size & no. of slots. But one gear has very large inertia. this gear is analogous to infinite bus bar (a huge alternator).

Now second gear is analogous to incoming alternator. If i want to connect incoming gear with the one having almost infinite inertia, i have to make incoming gear to run at same speed, in same sequence, and appropriate slot shift.

now if i join the above two, incoming gear starts floating with high inertia gear (alternator floating to infinite bus bar).

Now if i want to make the floating gear to work as contributor (alternator), i will increase its input (alternators turbine input), so that it contributes in larger inertia gear's (infinite bus bar) torque (amps).

If i want to work floating gear as a load (motor), i will load its shaft. So that larger inertia gear have to give its torque (amps) to run that incoming gear at constant (synchronous) speed.

Now sir i'm not able of finding an appropriate analogous term for voltage...? may you could help