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Start by
Abdul Basit
08-13-2014 01:37 AM

System frequency increased 50 to 53 Hz

If system frequency increased 50 to 53 Hz, which of the following most effected Transformer, turbine, generator
08-13-2014 03:45 AM
Top #2
Aijaz Hussain
08-13-2014 03:45 AM
Gen manufacturers allow to operate Gens bet 47.5 ~ 52.5 Hz for 50 Hz system, running Gen with 53 for long time will be harmful, Trafos may also be affected but Turbine may not be effected
08-13-2014 05:54 AM
Top #3
Alan Maltz
08-13-2014 05:54 AM
Abdul, Most electrical equipment can tolerate 5% overspeed for short periods of time, as long as the V/Hz limit is not violated. You have to be more careful with turbines, each one has a different set of critical frequencies that must not be approached or maintained for very long. Blade tips may start oscillating, get overstressed, overheated, or start rubbing against stationary parts with catastrophic results.

08-13-2014 08:41 AM
Top #4
Krishnan S
08-13-2014 08:41 AM
I understand you are referring to 53 Hz operation under load condition.
setting frequency to 53 Hz , will add strain to the bearings of shaft at turbine to generator .If there is an issue it will be mechanical.
Mechanical strain can also reflect as bearing temperature rise.
Electrically V/f should be limited to within +/- 10% to avoid over fluxing.
It is opined that there is no cause for setting frequency greater than nominal value.

In case of sudden load throw off ,frequency will for a short period, rise to over 53 Hz before controls take over.
you must consider all this also before arriving at a decision.
08-13-2014 11:30 AM
Top #5
Ing. Ole Knudsen
08-13-2014 11:30 AM
This is an interesting theoretical question, and you are not likely to get a simple answer.

There are lots of aspects that can be affected.

- Why does this increase happen?
Is it because of a sudden drop in load, while some turbine speed controller remains stuck, or a reverse power relay fail to operate?
If the speed control is stuck, you will have to check for critical frequencies within the turbine and generator, and some motors driving variable torque loads may get overloaded, and that could again overload transformers if it persist for any extended time.
If the reverse power relay fails to isolate the turbine/generator, it could be the turbine that is most affected, due to lack of steam to cool the turbine blades while it keeps operating as a big whisker.
If it happens suddenly, it could affect motors, when they are forced to accelerate their loads while they are already near full load.
If there is not a corresponding increase in voltage, virtually all electro-mechanical equipment will see an increase in load current, and that will also affect transformers. So much more because the transformer impedance will increase, causing even further secondary voltage drop, increasing load current even more.
If there is a corresponding voltage increase, it will in general be heat elements, and incandescent lighting that will be affected, and in some circumstances electronic equipment, that may have a narrower voltage tolerance.
As a curiosity, first generation TV sets will start to go funny, as they had their vertical scan locked in with the mains frequency.

There are undoubtedly many other areas that will be affected, at various degrees depending on the rate of change in frequency, and on the duration of the deviation from 50Hz.
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