GENERATION
and the frequency is given by :
f= P*N /120
Now to produce the voltage at a high frequency, two things have to be increased :
Since the number of poles in this Alternator have increased (compared to two pole High-speed turbogenerators rotating at 3000/3600 RPM at 50/60 Hz respectively), the diameter of the machine will increase which will make the size of machine large.
Now that to produce power at a High frequency, you would have to rotate the machine at high speeds which would require higher steam input for the same amount of power at a higher frequency.
The Higher input to alternator will deteriorate it mechanically. To paraphrase a high-frequency alternator needs to be mechanically robust and thus will require a larger size and more material in construction.
TRANSMISSION
While C and G are shunt parameters of line *G being frequency independent*
If the voltage at high frequency is used to transmit power
Even in distribution, the high-frequency AC will not be that efficient :
- Power is generated from Synchronous machines (Alternators) which rotate at a particular speed called the synchronous speed is given by
and the frequency is given by :
f= P*N /120
Now to produce the voltage at a high frequency, two things have to be increased :
- Number of poles in machine
- Speed of machine
Since the number of poles in this Alternator have increased (compared to two pole High-speed turbogenerators rotating at 3000/3600 RPM at 50/60 Hz respectively), the diameter of the machine will increase which will make the size of machine large.
Now that to produce power at a High frequency, you would have to rotate the machine at high speeds which would require higher steam input for the same amount of power at a higher frequency.
The Higher input to alternator will deteriorate it mechanically. To paraphrase a high-frequency alternator needs to be mechanically robust and thus will require a larger size and more material in construction.
TRANSMISSION
- Coming to your actual questions about transmission of power at high frequency, We need to realize the model of transmission line
While C and G are shunt parameters of line *G being frequency independent*
If the voltage at high frequency is used to transmit power
- Drop across inductor will increase as V = I*X =I*2*3.14*f*L (f being the frequency).
- A higher drop will cause the line voltage to sag.Hence the coveted flat voltage profile will not be obtained.
- The voltage will decrease with increase in length and it will be less most at the receiving end (where it is needed the most).
- Corona loss is directly proportional to frequency, hence the losses due to corona will increase
- This will cause more interference with communication/telephone lines.
- High losses in transmission wires due to skin effect.
- Because of skin effect, the cost of conductor material will increase as the conductor is not utilized fully at high frequencies.
- The economy of transmission is a major point while designing transmission lines. increasing the cost of the conductor will make the system uneconomical
- Since the resistance due to skin effect increases ( assume Rac=1.6Rdc), line losses (I^2R ones) will increase and hence the power transmission capability will decrease
- FACTS devices or compensators will be required for reactive power demand/supply making the system even more costly.
Even in distribution, the high-frequency AC will not be that efficient :
- We use a lot of power electronic devices. A high frequency will cause large switching losses.
- Harmonics of higher frequencies being fed back to the grid , filter requirements might be there.
- Poor voltage regulation
- Possibility of thermal noise/shot noise /white noise (high frequency ) interference with home appliances
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