function of protective relying

 function of protective relying

the various functions of protective relaying are : 

1- the prompt removal of the component which is behaving abnormally by closing the trip circuit of circuit breaker or to sound an alarm

2- to disconnect the abnormally operating part so as to avoid the damage or interference within effective operation of the rest of system

3- to prevent the subsequent faults by disconnecting the abnormally operating part

4- to disconnet the faulty part as quickly as possible so as to minimize the damage to the faulty part itself. for example, there is a winding fault in a machine and if it presists for a long time then there is a possibility of the damage of the entire winding. as against this, if it is disconnected quickly then only few coils may get damage instead of entire winding

5- to restrict the spreading of the effect of fault causing least interference to the rest of the healthy system. thus by disconnecting the faulty part, the fault effects get localised

6- to improve the system performance, system reliability, system stability and service continuity.

the fault can not be completely avoided but can be minimized. thus thr protective relying plays an important role in sensing the faults, minimizing the effects of  faults and minimizing the damage due to the faults

high voltage bushing

 Bushing is defined as a structure carrying one or several conductors through a partition such as a wall or tank etc. and insulating it or them therefrom

 A bushing has to provide : 

- Electrical insulation to the conductor for the working voltage and for various over voltages, which occur in service.

 - Mechanical support against various Mechanical forces.

TYPES OF BUSHINGS

1.1 Application

i) Alternator bushing
ii) Transformer bushing
iii) Bushings for switch gear
iv) Wall bushing or roof bushing
v) Cable end and joint box bushing

1.2 Application:
i) Indoor type
ii) Outdoor type

2.1 Type of Bushing:
n i) Stem type
n ii) Pull-through type

2.2 Type of Bushings:
n i) Condenser core type
n ii) Non-condenser core type
(Hollow Porcelain type)
n iii) Gas filled bushing
n iv) Solid Bushing

Solid Ceramic Bushing

 Epoxy Bushing

3. Type of insulation used in manufacturing Condenser Bushing :

i) Synthetic Resin Bonded Paper (SRBP)
• Oil filled
• Compound filled

ii) Oil Impregnated Paper (OIP)
• iii) Resin impregnated Paper (RIP)

Fuses and Circuit Breakers

 Fuses and Circuit Breakers ;

Fuses and circuit breakers are used to protect equipment or wiring against excessive current. For example, in your home, if you connect too many appliances to an outlet, the fuse or circuit breaker in your electrical panel “blows.” This opens the circuit to protect against overloading and possible fire. Fuses and circuit breakers may also be installed in equipment such as your automobile to protect against internal faults. Figure 2–29 shows a variety of fuses and breakers.

Fuses use a metallic element that melts when current exceeds a preset value. Thus, if a fuse is rated at 3 A, it will “blow” if more than 3 amps passes through it. Fuses are made as fast-blow and slow-blow types. Fastblow fuses are very fast; typically, they blow in a fraction of a second. Slowblow fuses, on the other hand, react more slowly so that they do not blow on small, momentary overloads.

Circuit breakers work on a different principle. When the current exceeds the rated value of a breaker, the magnetic field produced by the excessive current operates a mechanism that trips open a switch. After the fault or overload condition has been cleared, the breaker can be reset and used again. Since they are mechanical devices, their operation is slower than that of a fuse; thus, they do not “pop” on momentary overloads as, for example, when a motor is started.

Electric car

An electric car is powered by an electric motor instead of a gasoline engine. The electric motor gets energy from a controller, which regulates the amount of power—based on the driver’s use of an accelerator pedal. The electric car (also known as electric vehicle or EV) uses energy stored in its rechargeable batteries, which are recharged by common household electricity.

Electric cars produce no tailpipe emissions, reduce our dependency on oil, and are cheaper to operate. Of course, the process of producing the electricity moves the emissions further upstream to the utility company’s smokestack but even dirty electricity used in electric cars usually reduces our collective carbon footprint.

eddy current

 eddy current

When current is induced in a conductor such as the square piece of metal , the induced current  often flows in small circles that are strongest at the surface and penetrate a short distance into the material. These current flow patterns are thought to resemble eddies in a stream, which are the tornado looking swirls of the water that we sometimes see. Because of this presumed resemblance, the electrical currents were named eddy currents. 

Eddy currents are often generated in transformers and lead to power losses. To combat this, thin, laminated strips of metal are used in the construction of power transformers, rather than making the transformer out of one solid piece of metal. The thin strips are separated by insulating glue, which confines the eddy currents to the strips. This reduces the eddy currents, thus reducing the power loss.

dc machine

 dc machine

D.C. machines are the electro mechanical energy converters which work from a d.c. source and generate mechanical power or convert mechanical power into a d.c. power. These machines can be broadly classified into two types, on the basis of their magnetic structure. They are,

1. Homopolar machines
2. Heteropolar machines.

PDF

Circuit breaker Data Sheets

data sheets of circuit breaker :

- manufacturing

- type of circuit breaker

- rated voltage

- rated lighting impulsed withstand voltage

- rated normal current

- rated duration shot circuit

- rated short circuit breaking current

- press.for interruption ( at 20 )

- mass of complete circuit breaker

- mass of sf6 gas

- rated supply voltage

- year of manufacture