Electric Power Transmission Network Explained
The electrical power generated
in a power station situated in a remote place is transmitted to different
regions for domestic and industrial uses. Here we discuss the electric power
grid, power generation, transmission, and distribution.
Power Grid
What is a power grid?
The power grid forms a bridge
between electrical suppliers and consumers through interconnected networks.
The electrical power grid
consists of three main parts:
○ Generating plant for electric power.
○ Transmission of the electric power.
○ Distribution of the electric power.
Electrical Power Generation in Power Stations
Normally, electric power
generating plants are located near the source of power generation like dams,
coal mines, etc. They may be in remote locations, and the generated power has
to be supplied to the consumer in the city.
Sources for Power
Generation:
The following types of
resources are available for generating electrical energy for distribution:
○ Conventional Methods
1.Thermal:
Thermal energy or Nuclear
Energy used for producing steam for turbines which will drive the alternators
(rotating AC generators).
2. Hydro-Electric:
Potential of water stored at
higher altitudes is utilized as it is passes through water turbines which drive
the alternators.
○ Non- Conventional Methods:
1. Wind Power:
High velocities of wind are
utilized in driving wind turbines coupled to alternators.
Sources of Power Generation
Transmission of Power
Transmission of Electric Power
Once the power is generated
from the alternator, it is send to the typical substation in the power plant where they step up the voltage by
using the step-up transformers for transmission purposes.
As the voltage is stepped up,
it reduces the transmission losses. It is then sent to the power grid from
where it is then transmitted to different cities. All the power generated in
different places by different methods is stepped up and sent to a common place
called the grid.
Why do we need to step up
the voltage for transmission?
For long distance
transmission, power lines are made of conducting material like aluminum. There
is always some power loss associated with these lines.
If I is the current through
the wire and R is the resistance, a considerable amount of electric power (I2R)
is dissipated as heat. Hence, the power at the receiving end will be much less
than the actual power generated.
However by transmitting the
electrical energy at higher voltage, power loss can be controlled as is evident
from the following cases:
Case 1:
Power Transmitted At Lower
Voltage:
A Power of 11,000 Watts is
transmitted at 220 Volt.
Formula for Power (P) = V × I
V-Voltage
I-Current
Therefore, Current (I) =P / V
Current (I) =11,000 / 220.
Current (I) =50 Ampere.
If R is the Resistance of the
line wire,
Then the power Loss:
Formula, Power Loss = I2 × R
Power Loss = 502 × R watts = (25000
× R) Watts.
Case 2:
Power Transmitted At Higher
Voltage:
If 11,000 Watts power is
transmitted at 22,000 Volt
Current (I) =P/V =
11,000/22,000 =0.5 Ampere.
Power loss = I2 × R = (.5)2× R = (0.25
× R ) watts.
From the case 1 and 2, we
found that when the power is transmitted at higher voltage, the power losses
are less. Hence it is evident that if power is transmitted at a higher voltage,
the loss of energy in the form of heat can be considerably reduced.
For transmitting electric
power at 11,000W at 220 V the current capacity of line wire has to be 50 A and
if transmission is done at 22,000V it is only 0.5 A.
Thus for carrying larger
current (50A), thick wires have to be used. This increases the cost of
transmission to support these thick wires, and stronger poles have to be
erected, which further adds on to the cost. On the other hand, if transmission
is done at high voltages, the wires required are of lower current carrying
capacity, so thicker wires can be replaced by thin wires, thus reducing the
cost of transmission considerably.
An example would be if 400MW
power is produced at 15,000V in a power station, it could be stepped up to
230,000V before transmission. The power is then transmitted through the
transmission lines or network to the power grid.
Power Grid
Distribution of Electric Power
The electric power grid
connects different parts of the country. And the grid distributes the power to
the different parts of the country or state through the transmission lines or
network connecting different cities.
Outside the city, the
transmitted power from the grid is stepped down in voltage to 110,000 Volt from
230,000 Volt by a step-down auto transformer. Again the power is stepped down
to 11,000 Volt from 110,000 Volt by a Step Down power transformer located in
the streets and it is distributed to the industrial uses.
Finally before distribution to
the domestic user, the power is stepped down to 230 V or 440 V depending upon
the needs of the domestic user.