Politcal Satire cartoon on LOKPAL Bill in Newspapers

EENADU:

THE HINDU:

Beautiful Images from NASA

Some of the beautiful images from NASA

Gas Insulated Substation (GIS)

Gas Insulated Substations(GIS) is a compact, multicomponent assembly enclosed in a ground metallic housing which the primary insulating medium is compressed sulphur hexaflouride(SF6) gas. It generally consists components Of
a) Bus bars
b) Circuit Breakers
c) Disconnecting switches
d) Earthing switches
e) Current transformers
f) Voltage transformers
g) Cable and boxes
h) Gas supply and gas monitoring equipment
i) Densimeters and
j) Local control


Why we need GIS
1) Gas insulated Substations have found a broad range applications in power systems over the last three decades because of their high reliability Easy maintenance, small ground space requirements etc.,.
2) In our country also few GIS units have been in operation and a large number of units are under various stages of installation.
3) Although GIS has been in operation in several years, some of the problems are needful attention
4) These problems include VFTO during switching operations or earth faults and transient enclosure voltages and particle contamination.


Advantages of GIS:
a) Because of the entire equipment being enclosed in enclosures, filled with pressurized SF6 gas, installation is not subject to environmental pollutions, as experienced along coastal areas or certain types of industries.
b) Such installations are preferred in cosmopolitan cities, industrial townships, etc., where cost of land is very high and higher cost of SF6 insulated switchgear is justified by saving due to reduction in floor area requirement. It is not necessary that high voltage or extra high voltage switchgear to be installed out doors.
c) Since most of the construction is modular and the assembly is done in the works, one site erection time both for supporting structures and switchgear is greatly reduced.

Disadvantages with Air Insulated Substations:
a) It requires huge amount of area .
b) Each and every component of substation is exposed to air and pollution.
c) Particularly in coastal area all the insulators are exposed to air and saline contamination.
d) Frequent flashovers and breakdown occurs.
e) Maintenance cost is more.
f) Installation time is also more.
g) More concrete work is necessary.

A) The necessity of this study :
Extremely high dielectric properties of SF6 have long been recognized. Compressed SF6 has been used as an insulating medium as well as arc quenching medium in electrical apparatus in a wide range of voltages.
Gas Insulated Substations (GIS) can be used for longer times without any periodical inspections. Conducting contamination (i.e. aluminum, copper and silver particles) could, however, seriously reduce the dielectric strength of gas-insulated system

B) The origin of these particles :
Metallic particles in GIS have their origin mainly from the manufacturing process or they may originate from moving parts of the system, such as breakers and disconnectors.
Metallic particles can be either free to move in the GIS or they may be stuck either to an energized electrode or to an insulator surface (spacer, bushing etc.).
1) Different metallic contamination viz Cu, Al and Ag have been considered for the above study. Typically a GIB of inner and outer dia 102/292mm have been considered for a 245KV system.
2) Wires of radii varying from 0.1 to 0.5mm and length from 1mm to 10mm have been used for simulation. Co-efficient of restitution and pressure have been varied from 0.1 to 0.9 and 0.1Mpa to 1Mpa respectively.
3) Typical results show that for a variation of copper particles of radii from 0.2 to 5mm, the maximum radial movement reduces from 6mm to 1mm.
4) Whereas in the case of variation of length from 1mm to 16mm the radial movement increases from 1mm to 9.8mm. With the change of pressure the movement is found to be almost same for majority of particles considered

If a metallic particle crosses the gap and comes into contact with the inner electrode or if a metallic particle adheres to the inner conductor, the particle will act as protrusion on the surface of the electrode, and the voltage required for breakdown of the GIS will be dramatically decreased.
A metallic particle stuck on an insulator surface in a GIS will also cause a significant reduction of the breakdown voltage
Depending on the shape of the particles, as well as the geometry and voltage levels of the system, the particles get more or less influenced by the electric field which, in turn, makes them hazardous to the electrical system, in terms of partial discharges and breakdown.

1. The introduction of SF6 gas has revolutionized not only the technology of circuit breakers but also the layout of substations.
2. The dielectric strength of SF6 gas at atmospheric pressure is approximately three times that of air.
3. It is incombustible, non toxic, colourless and chemically inert.
4. It has arc-quenching properties 3 to 4 times better than air at equal pressure.
5. This enables the substation to be laid in a much lesser space.
6. Space requirement is only 10 to 25 percent of what is required is a conventional substation.
7. Thus where creation of a substation becomes necessary but adequate space is not available, such as in big cities or otherwise highly populated areas, GIS is the solution 

Importance of Electrical Engineering

Electrical energy is the most convenient form for transporting thousands of kilometers without much loss. Therefore it became the popular form of energy for utilization to increase the production and progress. The mechanical energy cannot be transmitted with ease without any loss in transmission. When generation, transmission and distribution became popular in the world, the fate of the human beings on he surface of earth change. It let to opening of so many industries and production of the goods. Therefore the productivity increased. Whatever the progress we see around us during 200 years of human history is mainly due to electricity. The electricity has become so much important in the human life without it man cannot lead his life comfortably, few moments of interruption in electric supply causes so much in convenience in his life. Electrical machines are continuously running day and night to keep the progress alive. The progress of the country nowadays is measured in terms of electrical energy generating capacity of that country

Thermal Power Plant

Thermal power station

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An Introduction to MATLAB

gmrit-cse

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Political Satire cartoons in Newspapers

courtesy: eenadu & Sakshi newspapers

Political Satire cartoons on Gas rate hike in newspapers

An Introduction to Electrical Drives

Drives

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Principle of Operation of Transformer

Transformer

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Introduction to MATLAB

Matlab Mech Eee Lectures 1

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Principle of Operation of DC motor & Generator

Dc motors

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vector control of Induction motor drive

    In applications where high performance variable speed operation is required, only 

dc motors were extensively used due to the ease speed control. Separately excited dc 

motors were particularly popular in applications where fast torque response was required. 

However, dc motors have some generic disadvantages like, requirement of periodic 

maintenance. Unusable in explosive or corrosive environments due to sparking problem. 

Commutation is difficult at high currents and voltages and hence its use is limited to low 

power, low speed motors.

    These problems can be overcome by using induction motors, which have a simple 

and rugged structure. Further, they have a high torque weight ratio as compared to their 

dc counterparts.

    The field and the armature currents respectively can control the  flux and torque, 

independently in the case of dc motors. It is because of this inherent decoupling between 

the field flux and the armature current, one is able to achieve very good torque dynamics 

from dc machines. Unlike dc machines, there is no inherent decoupling between flux and 

torque producing components of the stator currents in the induction  machines. Therefore, 

achieving good torque dynamics in ac machines is not easy. However, nowadays, field 

oriented control or vector control techniques have been employed, which results in good 

torque dynamics of induction motors. 

    In this dissertation work all discussions relating to induction motors  are with 

respect to squirrel cage type induction motors only. The operation of the 3phase induction 

motor is based on Faraday’s law and Lorentz force on a conductor. According to 

Faraday’s law, if the flux linking a conductive loop varies as a function of time, then an 

e.m.f, which is proportional to the rate of change of flux, is induced in the loop there by 

forcing a current to flow in the conductive loop. In the case of induction  motor, the induced current in the rotor conductors interact with the air gap flux to produce the 

torque. As the rotor tries to catch up with the magnetic flux in accordance with the Lenz’s 

law, the rate at which conductors are cut by the magnetic flux is reduced. As a 

consequence the induced rotor currents decrease and the Lorentz force on the rotor 

conductors reduce. Evidently if the rotor conductors were to catch up with the magnetic 

flux then there would be no relative motion between the conductors and the flux, and this 

would result in zero rotor currents and zero torque. Therefore, for the induction motor to 

operate there must exist some relative speed between the flux and conductors, which is 

called the slip speed ωsl.
for more click here VECTOR CONTROL

Political Satire cartoon1

ayyarao's photostream on Flickr.

cartooinst sridhar known for his cartoons sketched one good political satire cartoon in eenadu newspaper dated 12th june 2011.

Support to Lokpal Bill

As you are aware that Govt. of India has put a condition that 25 Crores of People support is needed to implement The Lokpal Bill.  For this we just have to give a Toll Free Call to +91-22-61550789.  The Call gets disconnected automatically after 1 ring.  After giving a call to this number, you will receive a Thanks Message. Request to forward this mail to as many as possible to make our nation corruption free. Please do it once, Call the above number with NO CHARGES I did it.