3. 3
Electric Charge
• Some particles have electrical CHARGE; charge can be POSITIVE or NEGATIVE
• Charged particles exert FORCE on each other:
• LIKE charges REPEL
• OPPOSITE charges ATTRACT
4. Structure of Atom
4
• Two of the tiny particles that make up atoms — protons and electrons — are the
bearers of electric charge.
• Protons have positive charge, electrons have negative charge.
5. Current
5
• Electric current refers to the flow of the electric charge carried by electrons as they
jump from atom to atom.
• It is the flow of electric charges per unit time.
• It is measured in “Amperes” (A).
6. 6
More than 3mA
“Painful shock”
More than 10mA
Muscle contraction
“no-let-go” danger
More than 30mA
Lung paralysis –
usually temporary
1 Ampere = ?
Basic Electricity
7. Circuits
7
• Consists of a voltage source, a load, and a path for current between the source and
the load.
– A load is a device on which work is done by the current through it.
• Open circuits versus closed circuits.
8. Voltage
8
• Voltage is the electric potential difference between two points.
• The driving force that causes electrons to move through a conductor is called voltage
or electro- motive force (emf).
• It is measured in “volts” (V)
9. Resistance
9
• The opposition to the flow of current through the conductor is called resistance (R)
and is similar to friction as shown in fig.
• Like other forms of friction, resistance is responsible for creating heat and loss of
power.
• Resistance is measured in ohms (Ω).
• Resistance could be measured using an Ohmmeter.
10. 10
OHM’s Law
Current in a circuit is directly proportional to the applied voltage and inversely
proportional to the circuit resistance.
V = I R
11. Conductors
11
• Electrical conductors allow electric current to flow easily because of the make up of
their atoms.
• In a conductor, the outer electrons of the atom are loosely bound and can freely move
through the material when an electric charge is applied.
• Some good Conductors are as follows:
Gold (used for contacts)
Copper (used for cables)
Tungsten (lamp filament)
Steel (conduit and switches)
12. 12
• The opposite of a conductor is an insulator.
• An insulator opposes the flow of electricity. Insulators are important to keep us safe
from electricity.
• The wire that carries electricity to your computer or television is covered with a
rubber-like insulator that protects you from getting electrocuted.
• Good insulators include glass, the air, and paper.
Insulators
13. 13
Basic Electricity
• When a current is constant with time, we say that we have direct current, abbreviated
as DC
Alternating Current
• Alternating current (AC), is an electric current in which the flow of electric
charge periodically reverses direction
Direct Current
14. Single Phase
14
• Its basically a sine wave AC voltage and current. That is all that is usually required.
• Single phase is like domestic supply in your home.
15. 15
Three Phase
• A 3-phase circuit combines three alternating currents of the same frequency, each 120
degrees out of phase with each other.
16. 16
AC Power Supply Frequencies
• Frequency is defined as one cycle per second.
• The hertz (symbol Hz) is the unit of frequency in the International System of Units (SI).
18. 18
Electric Power
• A watt is the basic unit of electric power.
• One watt is also defined as the amount of work that is accomplished when a voltage of
one volt causes one ampere of current to pass through a circuit.
• This relationship between power, voltage, and current is expressed by the following
formula:
Power = Volts x Amperes
19. 19
Real & Reactive Power
Power factor is an energy concept that is related to power flow in electrical systems.
Real Power
• It is the power that is actually converted into useful work for creating heat, light
and motion.
• Real power is measured in kilowatts (kW).
Reactive Power :
• It is the power used to sustain the electromagnetic field in inductive and capacitive
equipment.
• Reactive power is measured in kilovolt-amperes reactive (KVAR).
20. 20
Power Factor
Apparent power
• It is the combination of real power and reactive power.
• Total power is measured in kilovolt-amperes (KVA)
Power factor (PF)
It is defined as the ratio of real power to total power, and is expressed as a
percentage (%).
P.F = Active power (Kwh) x100
Apparent power (KVA)
22. 22
Basics of Electricity - Transformer
• Transformer
– Device used for voltage transformation.
Types of Distribution Transformer
Local in S/S:
• If placed in Sub Station called Local.
Because of weight restrictions
transformers for pole mounting are not
above 500 KVA
Pole Mounted Transformer (PMT)
• If mounted on a utility pole, they are
called pole-mount transformers.
Pad Mounted Transformer:
• If the distribution lines are located at
ground level or underground, distribution
transformers are mounted on concrete
pads and locked in steel cases, thus
known as pad-mount transformers.
23. 23
Types of Distribution Transformer
PMT At Double Pole Structure
Local In S/S Pad Mounted Transformer
24. 24
Grid Station
• Place where transformer step down the Extra High Tension (132KV) to High Tension
(11KV)
Feeder
– First cable from Grid Station terminating at Sub station/RMU or at PMT is termed as 11KV
Feeder.
Auto Transformer 66/132
KV & 132/220 KV- 40 MVA
to 250MVA
Power Transformer
66/11 KV & 132/11 KV 10
MVA to 40 MVA
Circuit Breaker 400 V-11KV-
66KV-132KV-220 KV, OCB-VCB-
SF6-GIS
Isolators 11KV-66KV-
132KV-220KV
Conventional-GIS
Current Transformer
11KV-66KV-132KV-220KV,
50/5 to 3000/5
Potentional Transformer 11KV-
66KV-132KV-220KV, 100-110
volts
Lightening Arrester 11KV-66KV-
132KV-220KV, Conventional-GIS
Capacitor Banks 11 KV 04
MVAR
Battery Banks 110 VDC, 220-
250 VDC
28. 28
Basic Electricity
• Circuit Breaker
It is an automatically operated electrical switch designed to protect an electrical
circuit from damage caused by overload or short circuit.
• Relays
A device designed to trip a circuit breaker when a fault is
detected.
OCB Switch VCB Switch
29. 29
Commonly Used Abbreviations
KEY TERMINOLOGIES ABBREVIATIONS
PMT Pole Mounted Transformer
MTL Mounted tower ladder
PPEs Personal Protective Equipments
SPEs Special Protective Equipment
SCADA Supervisory Control & Data Acquisition
ABC Aerial Bundled Cable
EHT Extra High Tension
HT High Tension
LT Low Tension
IBC Integrated Business Center
BOC Business Operation Center
You have often heard…
