Effect of supply Frequency
Frequency of the supply systems must be maintained constant
otherwise the following things get affected with frequency changes,
1. Electric lights do not operate
satisfactorily at lower frequency and give flickering. Hence the frequency must
be maintained constant for getting good lighting.
2. In case of A.C. motors, if the
frequency changes that causes the speed of motors to changes.
3. At lower frequencies in transformers
the number of flux linkages required is more, there by, more number of turns
and hence cost. The cost of 25 Hz transformers.
4. At higher frequencies say 50Hz, the
reactance of the lines and machinery is 2 times more than at 25Hz frequency. Due
to this poor regulation will occur. In case of long transmission lines, the charging
current limits the choice of transmission voltage. From the above effects it is desirable to
choose a constant frequency we are adopting is 50Hz and in America 60 Hz is as
a standard frequency.
Transmission Lines: The transmission lines are mainly
used to deliver bulk power from power stations to the load centers and large
industrial consumers. Depending upon the operation voltage these are mainly
divided into two types, namely
Distribution Lines: Distribution lines are used to
deliver the power from substation, to the various consumers. Depending upon the
operation Voltage, these are mainly dived into two types, namely
Effect of supply voltage
on Transmission Lines
In transmission lines more troubles
are experienced with heavy currents as compared to higher voltages. Hence
greater security, some times lower maintenance and operating costs may be
obtained by designing the transmission lines at higher operating voltages.
Due to increase in operating voltage,
the cost of line supports increase slightly and spacing between conductors also
increases, the size of conductors is reduced because the current is reduced and
hence the percentage regulation in the lines is reduced.
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