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Gate paper EE 2008to 2015

    SEE PDF LINK  BELOW :-

•        2008   pdf  see:-

                  https://dochub.com/winaymehta/mVVOKp/ee-2008#

•         2009 pdf  see :-

                  https://dochub.com/winaymehta/wkkOZm/ee-2009?pg=2

•        2010 pdf  see :-

              https://dochub.com/winaymehta/NWWEZ3/ee-2010

•        2011 pdf see :-

             https://dochub.com/winaymehta/MbbpK1/ee-gate-2011

•        2012 pdf  see :-

             https://dochub.com/winaymehta/J33Lnx/ee-gate-2012?googleDocExists=true

•        2013 pdf  see :-     

             https://dochub.com/winaymehta/J33Lnx/ee-gate-2012?googleDocExists=true

•         2014 pdf  see :-

1.   https://dochub.com/winaymehta/5RRNED/ee-gate-14-paper-01    

     

1.    https://dochub.com/winaymehta/jYY836/ee-gate-14-paper-02

1. https://dochub.com/winaymehta/a11DZW/ee-gate-14-paper-03

•    2015 pdf see :-

1.           https://dochub.com/winaymehta/NWWJK9/ee-gate-15-paper-01_new2
2.      https://dochub.com/winaymehta/ljjRnl/ee-gate-15-paper-02_new2                                                                                                        

           

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INSTRUMENT TRANSFORMERS

                 

INSTRUMENT TRANSFORMERS

These are special type of transformers used for

the measurement of voltage, current, power and energy.

As the name suggests, these transformers are used in conjunction with the relevant instruments such as ,

Ammeters, Voltmeters, Watt meters and energy meters.

Such transformers are of two types :

• Current Transformer (or Series Transformer)
• Potential Transformer (or Parallel Transformer)

CUREENT TRANSFORMERS

A current transformer is an instrument transformer which is used to measure alternating current of large magnitude by stepping down by transformer action. The primary winding of CT is connected in series with the line in which current is to be measured and the secondary is connected to the ammeter.

      Measurement of current as CT :-

             The primary winding is so connected that the current to be measured passes through it    and the secondary is connected to the ammeter .

             The function of CT is to step down the current.

                

                     POTENTIAL TRANSFORMERS

       

Potential transformers are used where the voltage of an AC circuit exceeds 750V as it is not possible to provide adequate insulation on measuring instruments for voltage more than this.

       

       Measurement of voltage by PT:-

The primary winding is connected to the voltage side to be measured and secondary to the voltmeter. The function of PT is to steps down the voltage to the level of voltmeter.      

             

      

GAS CIRCUIT-BREAKER

              GAS CIRCUIT-BREAKERS

   

       

SF6 circuit breaker is equipped with separated poles each having its own gas. In all types of the circuit

breakers, gas pressure is 2 bars (absolute 3 bars). Even if the pressure drops to I bar, there will not be any change

in the breaking properties of the circuit breaker due to the superior features of SF6 and Elimsan's high safety factor

for the poles. During arcing, the circuit breaker maintains a relatively low pressure (5-6 bars) inside the chamber

and there will be no danger of explosion and spilling of the gas around. Any leakage from the

chamber will not create a problem since SF6 can undergo considerable decomposition, in which some of toxic

products may stay inside the chamber in the form of white dust. If the poles are dismantled for maintenance, it needs

special attention during removal of the parts of the pole. This type of maintenance should be carried out only by the expertsof the manufacturer.

VACUUM CIRCUIT BREAKER

                                                             

Circuit Breakers:                 

Designed for use with air insulated metal enclosed switchgear and

controlgear and indoor applications. EVK CB’s are suitable to rapid auto-reclosing.

The switching tests of breaker were carried out inside MME* type cubicle.Vacuum circuit-breakers does not require an interrupting or insulation medium. In fact, the interrupters do not contain ionizable material.

During the separation of current-carrying contacts, contact pressure reduces, real contact surface reduces and the temperature of contacts increases to melting temperature. This produces metal vapours which initiates and supports the vacuum arc, maintaining until the next current zero. Due to the special geometry of the spiral contacts, the arc column is kept rotating by the radial magnetic field produced in order to involve a wider surface than that of a fixed contracted arc. Thus, overheating and erosion of the contacts are prevented. So the lifespan of circuit breaker is increased.

                                         

                  

Flip- Flop

flip- flop  :-

              A flip-flop is a bistable multivibrator. The circuit can be made to change state by signals applied to one or more control inputs and will have one or two outputs.

           SR latch operation   

     
     Characteristic table              Excitation table

S    R    Q_next   Action                Q    Q_next      S      R        

0     0     Q       hold state            0      0          0      X
0     1     0        reset                    0      1          1      0
1     0     1        set                       1      0          0      1
1     1    X      not allowed          1       1         X      0

           JK latch    

The JK latch is much less frequently used than the JK flip-flop. The JK latch follows the following state table:

           JK latch truth table

     J   K     Q_next     Comment

     0   0      Q         No change

     0   1       0         Reset 

     1   0       1         Set

     1   1       Q         Toggle

Substation

   
           

TRANSFORMER COMPONENTS

• Tank

The transformer tank or enclosure of a power transformer is fabricated of welded

steel. The tank contains the transformer core and coil assembly. It is normally filled

with mineral oil or a synthetic nonflammable insulating liquid that is used as an

insulating and cooling medium.

• Bushings

The electrical power circuits must be insulated where they enter the tank. A bushing

provides an insulated oil-tight and weather-tight entrance for the conductor into the

transformer. It is usually composed of an outer porcelain body, and at higher

voltages, additional insulation in the form of oil and wound paper is used within the

porcelain column.

• Conservator

On larger transformers (over 500 KVA), a reservoir of oil is maintained in a tank at a

level above the cover of the transformer which is connected to the transformer by a

pipe. This is known as a conservator tank (expansion tank) and keeps the main tank

completely full of oil at all times, permitting expansion and contraction. An oil level

indicator with an alarm circuit is provided to indicate the oil level in the conservator

tank.

• Breather

The conservator tank has a breather to the outside. In order to take care of the

expansion and contraction of the cooling liquid with varying temperatures, smaller

units have an air space above the oil, which is connected to atmosphere by a breather.

This breather is, arranged to prevent the entry of moisture, snow, etc, into the

transformer

• Radiators

Radiators are fitted to the tank so that a larger surface is reached by the liquid

flowing into the top, down the tubes of the radiators and back into the bottom of

the transformer.

• Cooling fans

Fans blow air across the radiators to increase the cooling of the oil.

• Off Load Tapchanger (OLTC)

To change the turns ratio on the source winding, a switch is operated by a handwheel

on the exterior of the tank. The handwheel is used to operate a switch within the

tank via an exterior operating rod and interior insulated operating rods. The switch

takes the form of fixed terminals or contacts arranged in a circle. Turning the

handwheel moves the contact or finger around the centre of the circle to complete