Hi guys,
I have a question. A power station is generating 100MW,3phase
50Hz at 440KV that must be connected to a grid of 220KV at 60HZ. How
can this be done.Like the step down thing can be done with a
transformer thing but how about the frequency change.Is this possible.
Thank You,
Prizark
I know of a couple ways that this is done. The old school way is to
connect the shafts of two synchronous machines that have different
numbers of poles. Such as one with 10 and the other with 12. That
way one will run at 60Hz and the other at 50Hz, with the same rotor
speed. The current in the field windings is controlled to set one
machine as the generator and the other as the motor. Power can be
made to flow in either direction. I have heard of large stations like
this, I believe in Japan where part of the grid is on 60Hz and part on
50Hz. (I may be wrong about where these things are located)
The more modern method is to rectify the 50Hz station output, like for
a DC transmission line, then an inverter converts this to whatever
voltage and frequency you like at the other end. This allows better
efficiency but is much more complicated to control. The way this is
put together is much more complicated than this description, but if
you look up how DC transmission lines work you should find something
more usefull.
Either technique is primarily for changing the frequency, and is also
used to control power flow. Both methods will use transformers to
raise the voltages. Sychronous machines and the thyristors used for
the rectifier/inverter generally run at lower voltages (~10kV).
Ethan