header PART 01: Fundamental Idea Of Electricity

PART 01: Fundamental Idea of Electricity

01. Source of Energy:

The Sun, Water Flow, The Wind, Fuels, Nuclear Energy & Water Flow.

02. Current:

The Flow of free electrons (or charge) in a definite direction is called Electric Current expressed in ampere (I). Moreover, when electric pressure or voltage is applied, the free electron negatively charged start moving towards the positive terminal.

03. Measurement of Current:

Current is measured by the time rate of flow of charge through the conductor.

I=q/t [I=Current, q=Flowing charge, t=time]

04. Type of Current:

Current are two types. (a) AC current (b) DC Current

AC Current: AC stands for “Alternating Current,” meaning current that changes polarity or direction, respectively, over time.

DC Current: DC stands for “Direct Current,” meaning or current that maintains constant polarity or direction, respectively, over time.

05. HVDC:
High Voltage Direct Current is used to transmit bulk amount of electric power. No frequency effect in HVDC. No equipment or substation is require between the transmission line. So that the cost of transmission will be lower.
There is an HVDC transmission line between India to Bangladesh to transmit 500MW of power though Veramara.

06. Voltage:

Voltage is the electromotive force or the electric potential energy difference between two points (often within the context of an electrical circuit) per unit of charge, expressed in volts (V).

07. Electromotive Force (EMF):

There is distinct difference between EMF and Voltage (potential difference). Electromotive force, abbreviation E or emf, is a measure of energy that is imparted by a energy source, such as an electric generator or a battery gives to each coulomb of charge.

08. Resistance:

The resistance of a conductor is defined as the ratio of potential difference applied its ends to the resulting current through the conductor.

R= V/I

In other word, Resistance is an opposition to the flow of current.

09. Resistivity:

The resistivity or specific resistance of a material is the resistance provided by 1 meter length of wire material having area of cross section of 1msquare.

10. Effect of Temperature on Resistance:

In the normal range of temperatures, the resistance of a metalic conductor increases linearly with the rise in temperatures.

11. Insulation Resistance:

An insulated current carrying conductor or electrical equipment may have some leakage current. Insulation resistance is that resistance which provide guard to the leakage current.

In other word, we can say that Insulation resistance is the resistance of a conductor, cable or electric equipment.

12. Capacitance:

When two charged metal plate or conductor separated by an insulating material (called dielectric material) then the capacitor is formed. The properties of stored charge of a capacitor is called capacitance.

In other word, capacitance is the ratio of the change in electric charge of a system to the corresponding change of its electric potential.

13. Electric Power:
The power of an electric appliance is the rate at which electrical energy is converted into other forms of energy.

Mathematically, the multiplication of voltage and current is the power.

P=VI

14. Type of Power:
There are three types of power.
(a) Active Power
(b) Reactive Power
(c) Apparent Power

For Single Phase:

15. Kilowatt Hour:

Kilowatt Hour is a measure of electrical energy to a power consumption in one thousand watts for one hour.

1 KHW= 1 KW x 1 Hour

16. Electrical Energy:
The loss of potential energy in maintaining current in a circuit is called Electrical Energy consumed in the circuit.

17. Inductance:
The flow of electric current creates magnetic field around the conductor. Inductance is the tendency or properties of electric conductor to oppose a change in the electric current flowing through it. It is denoted by L.

18. Impedance:
Impedance is the combine effect of resistance, inductance and capacitance.

19. Different Type of Voltage Level:
(a) Rated Voltage: The maximum voltage that can be produce by a generating station under safety margin.
(b) Nominal Voltage: The predetermined system voltage to a circuit is called nominal voltage.
(c) Extra low voltage: The voltage level below 70 Volt
(d) Low Voltage: The voltage level from 70 Volt to 600 volt
(e) Medium Voltage: The voltage level from .6KV to 33KV
(f) High Voltage: The voltage level from 33KV to 220KV
(g) Extra High Voltage: The voltage level from 220KV to 760KV
(h) Ultra High Voltage: The voltage level above 800KV

20. Different Voltage Level in Bangladesh:

(a) Generation Voltage: 11KV

(b) Transmission Voltage: 132KV, 230KV, 400KV

21. Flow diagram of Generation to Distribution Network:

22. Advantages of High Voltage Transmission:
(a) In high voltage current is low. So that the conduct size will be lower which is reduce the transmission cost.
(b) Low line current in high voltage transmission leads the lower voltage drop. (V=IR)
(c) Lower Power loss (Power loss=I2R)
(D) Transmission efficiency also higher.

23. Electrical Material:

The material used in electricity and electronics are broadly divided into three major types.

(a) Conductors

(b) Semiconductors

(a) Conductors:

(i) Conductors are formed by metalic bonds. These bonds are based on a structure of positive metal ions and surrounded by a cloud of electrons.

(ii) Conductors have positive temperature of coefficient.

(iii) Conductors are used o carry current in electric circuit.

(b) Semiconductors:

(i) Semiconductors are formed by covalent bonds.

(ii) Semiconductor have negative temperature coefficient.

(iii) Semiconductors are used in the manufacturing of electronics device.

(c) Insulators:

(i) Insulators are predominantly covalent compounds. The valence electrons are tightly locked with the neighboring atom and are not available to support the flow of current.

(ii) Insulator have negative temperature of coefficient of resistance.

(iii) Insulator are used to confine the current tot the desired path.