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Rehman
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Join Date: Jul 2013
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Electromechanical Transients

05/01/2014 2:08 PM

Can anybody tell me the reason of generating the electromechanical transients and why are they below power frequency. Thanks
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lyn
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#1

Re: Electromechanical transients

05/01/2014 2:22 PM

Electrical Engineer's Reference Book

Electrotek Concepts - Transient Studies

basic concepts of electromagnetic transients program - SARI

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Rehman
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#5
In reply to #1

Re: Electromechanical transients

05/03/2014 2:04 AM

Thanks, God bless you
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RAMConsult
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#2

Re: Electromechanical Transients

05/01/2014 4:01 PM

It's actually an advanced phenomena known as Subsynchronous Resonance. They are below synchronous speed because with transients it's the longer time constant system that dominates, in this case the mechanical systems vs. the electrical systems. Every physically realizable system has the potential for resonance as their dynamic effects interact with each other.

In the case of a power system quite a few things affect the position of the rotor, the governor, excitation system, and the load. As the loads are constantly shifting, the governor tries to follow them, as the voltage is constantly changing, the AVR tries to correct it, thus the posistion of the shaft is being constantly jerked around. If the perturbances start building to resonance the forces become huge and can actually shatter the shaft between the generator and the turbine. Google on "subsynchronous resonance" for lots more info.

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Rehman
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#6
In reply to #2

Re: Electromechanical Transients

05/03/2014 2:10 AM

Thank you
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pcchatur
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#3

Re: Electromechanical Transients

05/02/2014 5:28 AM

The rotor (shaft) system of cylindrical (horizontal) generator have their own natural frequencies which decides its "critical speed". One of the critical speed is "Torsional" critical speed. Whenever any electrical disturbance results in change of rotational speed (due to difference in applied torque and the load torque), another torque known as "synchronizing" torque is developed which tries to pull back the system speed to synchronous speed. This takes place at "disturbing" frequency. In this process, the systems "swings" around synchronous speed before coming to steady state condition. This "swing" is at natural frequency of the shaft system. If under any condition, disturbing frequency matches with natural frequency of the shaft system, then "electro-mechanical resonance" takes place. Under such conditions, shaft system may get seriously damaged.
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Rehman
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#7
In reply to #3

Re: Electromechanical Transients

05/03/2014 2:14 AM

Thanks
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StandardsGuy
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#4

Re: Electromechanical Transients

05/02/2014 11:04 AM

Is this homework? We are not here to short-circuit your education. Electromechanical transients are not usually generated on purpose. They have the frequencies of the mechanical devices. Your post is not stated completely. Give us more information on what you are doing.

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Rehman
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#8
In reply to #4

Re: Electromechanical Transients

05/03/2014 2:15 AM

Thanks
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