WANGLERACE: 2014

Friday, 27 June 2014

Structure of Electric Power System

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

WANGLERACE

Pages

Tuesday, 23 December 2014

Friday, 27 June 2014

Structure of Electric Power System