Generating
station
-Generates A.
C power
-Normal
generating voltage is 11kV
Types
-Steam power
station
-Nuclear power
station
-Hydroelectric
power station
-Electric
Power station
-Diesel Power
station etc..
Block Diagram
of Generating Station
The
generating voltage is stepped up using three phase step up t/f to 132kV in
generating station
ØPrimary
transmission:
132kV is transmitted by three phase three
wire overhead system. It goes up to receiving station.
ØSecondary
transmission:
Here the voltage is stepped down to 33kV
and it is transmitted. It ends at a substation.
ØPrimary
distribution:
33kV is again stepped down to 11kV and is
transmitted .This runs along the road sides of the city.
ØSecondary
distribution:
11 kV is stepped down to 400V.It forms
Secondary distribution. It is the three phase four wire system. Voltage across
any two phases is 400V and b/w phase and neutral is 230V.
Operating Voltages
1.Generating Voltages
6.6, 11, 13.2 or 33 KV
2. High Voltage
Transmission:
765, 220, 132, 66 KV
3. Primary Distribution;
3.3, 6.6 KV
4. Low-Voltage
Distribution:
AC - 400/230 V, 3-phase, 4-wire
DC – 400/230 V, 3-wire system
DC
TRANSMISSION
ADVANTAGES:
1. It requires only two
conductors and three for AC transmission
2. There is no inductance,
capacitance, phase displacement and surge problems
3. Voltage drop will be
less due to absense of inductance and voltage
regulation will be better
4. No skin effect
6. It has less corona loss
and reduced interference with communication circuits
7. No stability problems
and synchronising difficulties
DISADVANTAGES:
1.Electric power cannot be
generated at high dc voltage (5 MW)
2.It cannot be stepped up for
transmission
3.Switches and circuit
breaker have limitations
AC TRANSMISSION
ADVANTAGES:
1.The power can be generated
be high voltages (500 MW)
2.The maintenance of AC
sub-station is easy and cheaper
3.Step up and step down
transformer allows to transmit high voltages and distribute it at safe
potential
DISADVANTAGES:
1.It requires more copper
than dc line
2.Construction is more
complicated than dc
3.Due to skin effect the
total resistance in the line is increased
4.Ac line has capacitance.
There is a continuous loss of power due to charging current even when line is
open
