Showing posts with label Power System. Show all posts
Showing posts with label Power System. Show all posts

Wednesday, March 23, 2016

March 23, 2016

Skin Effect in Transmission Lines

The distribution of current throughout the cross section of conductor is uniform only when the steady current(D.C.) is passing through it. However, an alternating current flowing through the conductor does not distribute normally, rather it has the tendency to concentrate near the surface of the conductor as shown in figure below.
Skin effect

What is skin effect

The tendency of alternating current to concentrate near the surface of a conductor is known as skin effect. 
This results in higher resistance to alternating current that to direct current and is more pronounced as frequency is increased. This is known as skin effect. It causes a larger power loss for a given rms ac than the loss when the same value of dc is flowing through the conductor. Consequently, a qualitative explanation of the phenomenon is given below.

" A conductor could be considered as composed of very thin filaments. The inner filaments carrying current gives rise to flux which links the inner filaments only when as the flux due to current carrying outer filaments enclose both the inner as well as the outer filaments. The flux linkages per ampere to inner strands is more as compared to outer strands. The inductance* of each strand will vary according to its position. Thus the strands near the center are surrounded by greater magnetic flux and hence have larger inductance than that near the surface. The high reactance of inner strands causes the alternating current to flow near the surface of conductor. This crowding of current near the conductor surface is the skin effect. "
With the increase of the frequency the non-uniformity of inductive reactance of the filaments becomes more pronounced, so also the non-uniformity of current distribution. For large solid conductors the skin effect is quite significant even at 50Hz. The analytical study of skin effect requires the use of Bessel's functions.
The skin effect depends upon the following factors:-
  1. Nature of material
  2. Diameter of wire- It increases with increase in diameter of wire
  3. Frequency- It increase with increase in frequency.
  4. Shape of wire- It is less for stranded conductor than solid conductor.
It may be noted that skin effect is negligible when the supply frequency is low (= 50Hz) and conductor diameter is small (< 1 cm).
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Monday, March 21, 2016

March 21, 2016

Corona phenomenon in Transmission Lines

Corona phenomenon in Transmission Lines
When an alternating potential difference is applied across two conductors whose spacing is large as compared to their diameter, there is no apparent change in the condition of atmospheric air surrounding the conductors, if the applied voltage is low. However when the voltage on line conductor is raised beyond a certain limit, called critical disruptive voltage, the conductors are surrounded by pale violet glow together with a slight hissing noise and a smell of ozone. This phenomena is called as corona.

In short corona phenomena is the ionization of air surrounding the power conductors. Free electrons are normally present in free space because of radioactivity and cosmic rays. As the potential between the conductors is increased, the gradient around the surface of the conductor increases. Assuming that the spacing between the conductors is large as compared with the diameter of the conductors. The free electrons will move with certain velocity depending upon the field strength. These electrons will collide with the molecules of air and in case the speed is large they will dislodge electron from the air thereby the number of electrons will increase. The process of ionization is thus cumulative and ultimately forms an electron avalanche. This results in localization of air surrounding the conductor and hence corona effect is occurred.
Corona occurrence is therefore defined as a self sustained electric discharge in which the filed intensified ionization is localized only over a portion of the distance between the conductors.
The phenomena of corona is accompanied by hissing sound, production of ozone, power loss and radio interference. The higher the voltage is raised, the larger and higher the luminous envelope becomes and greater the sound, the power loss and radio noise. If the applied voltage is increased to breakdown value, a flash over will occur between the conductors due to the breakdown of air insulation.

If the conductors are polished and smoothed, the corona glow will be uniform throughout the length of the conductors, otherwise the rough points will appear brighter. With d.c. voltage, there is difference in the appearance of the two wires. The positive wire has uniform glow about it, while the negative conductor has spotty glow. For a visual corona the line voltage has to be somewhat higher than critical disruptive voltage and is called visual critical voltage.

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Friday, July 25, 2014

July 25, 2014

Power System


Energy plays a vital role in day to day life of human being for overall development of the country and the world. We know different forms of energy such as wind, solar, thermal, etc. Our dependency on energy is such that without it our life become somewhat cumbersome. For instance, if electricity goes off for a minute we stigmatize the Power Supply Authority.
Electrical Power System- Electicalfreaks.blogspot.in

Electrical Power System 

Electrical Power System- Generation, Transmission, Distribution
Electrical Power System-Generation, Transmission and Distribution
We need to understand that there aren't so much storage of coal, natural gas, so we had to move on Non Conventional Energy Sources e.g. wind, tidal, solar. 
There are various uses of Electrical Energy in different fields such as for domestic purpose, where it is used for heating, cooking, refrigeration, light etc. Also it is used in industries, commercial complexes, irrigation purposes, etc.

To satisfy everyone's need, supply utilities provide electrical energy via a network which is known as Power System. 
Block diagram of Electrical Power System- Electricalfreaks.blogspot.in

 As Law of Conservation states, energy can neither be created nor be destroyed, it can be converted from one form to another; power stations converts some of energy into electrical energy.
It mainly consist of two parts, one is turbine and other is alternator for example, turbine converts s\some form of energy into Mechanical form and then alternator converts it into Electrical form. The generated electricity is in the form of 3� which is step up in power station. Then it's transmitted to by transmission line over a long distance and then it's stepped down in distribution substation to utilization level. The step up and step down process is done by transformer. 
After that electrical energy is distributed to different consumers.


Meaning of few technical words:-
  • Step Up:- Increasing the magnitude of voltage without change in frequency by transformer.
  • Step Down:- Decreasing the magnitude of voltage without changing its frequency by transfromer
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Location: Chandrapur, Maharashtra, India

Monday, July 9, 2012

Civicon Limited will do the roads at LTWP for Ksh.3.2 Billion
July 09, 2012

Civicon Limited will do the roads at LTWP for Ksh.3.2 Billion



News just in confirm that Civicon Limited, a lading construction company has won the contract for the construction of access roads in the Lake Turkana Wind Farm and also a roads to the station.

The contract which is worth Ksh. 3.2 Billion will entail the construction of 109km on-site road network at another 204km access road. These roads will be built to gravel standards and should provide the
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Monday, May 24, 2010

Extra High Voltage Systems - 400kV Lines
May 24, 2010

Extra High Voltage Systems - 400kV Lines




Nominal Voltage 400kV
Cicuits per phase 1
Sub-conductors per phase 2
Span 400m
Conductor Name and Size Moose,54/3.53mm Alluminium 7/3.53mm Steel
Sub-conductor Diameter 3.177cm
Bundle Configuration Horizontal
Bundle Spacing 450mm
Interphase Spacing
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Wednesday, May 12, 2010

50kVA PMTx Substation Transformer
May 12, 2010

50kVA PMTx Substation Transformer



Name : 50kVA Pole Mounted Substation Transformer
Rating: 50kVA
Cooling: Oil Cooled
Application: Commercial,Heavy Residential,Farmhold

This type of transformer is mainly used for Step-Down purposes of voltages in the range of 11kV~415/240V.


Much of their kind are available for 3phase voltages though Single phases may also be available(need citation). The cooling system employed is Oil
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Saturday, April 24, 2010

Corona
April 24, 2010

Corona

Have you ever wondered why high voltage power lines buzz (zszszs sound)? Its because they are producing corona which is interacting with the surrounding air.
Corona is the process by which current, perhaps sustained, develops from an electrode with a high potential in a neutral fluid, usually air, by ionizing that fluid so as to create plasma around the electrode. The ions generated eventually
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Thursday, April 22, 2010

Power System Network
April 22, 2010

Power System Network






A detailed explanation of the conversion and distribution of electric energy from the power station to consumer units.This post describes how electric energy moves from the power generating station through conductors of various sizes to consumers premises.To minimize losses and for economical reasons, electrical energy has to be converted into different magnitudes during transmission and
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