POWER SYSTEM UTILIZATION
Subject code: EP 707
Introduction
Electric power utilization refers to the usage of electrical
energy by the end users.
Electric power plays a key role in achieving economic
growth and improving the quality of life
it is used in industrial and domestic building for various
purposes such as:
lighting
heating
cooling
running appliances and machinery.
Overview of electrical power sector in Libya
Unit 1
ELECTRIC HEATING
Heat is a thermal energy transferred between two
systems due to temperature difference
Types of heat transfer:
1. Conduction : through a solid or stationary fluid
2. Convection : between a surface and a moving fluid
3. Radiation : All surfaces of finite temperature emit
energy in the form of electromagnetic waves.
using heat-sensing cameras to detect
heating concentrations or heat leak
sources in electrical equipment.
A heat sink is a device that transfers
heat from a hot device to a cooler fluid
medium, where it is dissipated away
from the device
Unit 1
ELECTRIC HEATING
Electric heating is a process in which the electrical
energy is converted to thermal energy/heat
When current is passed through a resistive element,
heat is produced.
Power across resistor, P = I²R
Heat dissipated, H = P× 𝑡 = I²R t Joules
Electric heating applications:
1. Domestic applications
space heating
immersion heaters for water heating
hot plates for cooking
electric ovens
Electric kettles
dryer machine for clothes
Electric ironing
2. industrial applications
melting of metals
heat treatment of metal:
like annealing, tempering, soldering and brazing etc.
moulding of glass
Enamelling of copper wires
welding
electric tempering furnace Annealing
Electric brazing Induction brazing
PCB soldering
Enameling moulding of glass
ADVANTAGES OF ELECTRIC HEATING
Clean
Economical
Pollution free
Ease to control
High efficiency
Automatic protection
Safe
Better working conditions
Less floor area
Power frequency heating
providing heating by using 50Hz or 60Hz electricity
1. Resistance heating:
a flow of current through a resistor produces ohmic losses (I²R) which results in the
heating of the substance.
1.1 Direct resistance heating:
In this method the electric current is passed through the material to be heated, i.e. the
heat is produced in the charge itself.
This method is employed in:
Resistance welding
Electrode boiler for heating water
Salt bath furnace for heat treatment of
steel or light metal.
Electrode boiler for central heating
High voltage electrode boiler
Salt bath furnace
1.2 Indirect resistance heating:
in this method the heat produced by the heating element is delivered to the
charge by radiation or convection.
Applications:
Electric oven
Electric iron
Ordinary domestic radiators
Indirect resistance heating
Electric kettle
Heat treatment of metal
Electric oil radiator Resistance oven
2. Arc Heating
A high voltage applied across an air-gap, the air
becomes ionized and starts conducting in the form of
a continuous spark or arc thereby producing intense
heat. the temperature obtained is in the range of
3000°C- 3500°C. The electrodes are made of
carbon/graphite,
2.1 direct arc heating:
When supply is given to the electrodes, two arcs are
established and current passes through the charge, as
the arc is in direct contact with the charge and heat is
also produced by current flowing through the charge
itself. The main application of this type of heating is
production of steel. Direct arc furnace
2. Arc Heating
2.2 indirect arc heating:
in this method, arc is established between the two electrodes, the heat so
developed is transferred to the charge by radiation. This method is generally
used in the melting of non-ferrous metals.
Indirect arc furnace
High Frequency Heating
The main difference between the power-frequency and the high-frequency heating is
that: in the conventional methods, the heat is transferred either by conduction,
convection or by radiation, but in the high-frequency heating methods, the electro-
magnetic energy converted into the heat energy inside the material.
1. Induction Heating:
in induction heating the charge is heated by the induced currents that created by the
varying electromagnetic induction. It is based on the transformer working principle
“magnetic coupling”
Induction heating is the most advanced contactless method of transmitting
electrical energy to the object being heated, converting electrical energy directly
into thermal energy.
The depth of penetration of induced currents into the disc is given by:
Types of induction heating
i. Core type furnaces:
also known as a channel induction furnace, is a specific type of electrical furnace used
for melting metals. It operates on the principle of electromagnetic induction to
generate heat within the material without directly touching it.
Types of Induction Heating
ii. Coreless type induction furnace:
It is a simple furnace with the absence core. In this furnace, heat developed in the
charge due to eddy currents flowing through it.
Block diagram of induction heating control system
2. Dielectric Heating
Also called high frequency capacitive heating
Also known as radio frequency heating
When a non-metallic material such as wood, plastic or ceramic is subjected to an
alternating electrostatic field, then dielectric loss occurs in it.
This loss appear in form of heat and known as dielectric heating.
Operating voltage: 500-3000 V
Operating frequency: 10 MHz – 40 MHz
Dielectric heating finds applications in hyperthermia cancer treatment, pain relief
through diathermy, and even sterilizing medical instruments. Its targeted heat
delivery minimizes damage to surrounding tissues.
3. Infrared heating:
In this method of heating, heating elements consist of tungsten filament lamps
together with reflectors to direct the whole of heat emitted on to charge in the form
of electromagnetic radiation without heating the air in between.
The heat emission intensity obtained is about 7000 W/m² as compared to 1500
W/m² obtained with ordinary resistance furnaces.
Infrared heating is used for paint drying
for various dehydration and other processes.
for low temperature heating of plastics
Electromagnetic Spectrum
Microwave Heating
Microwave Applications:
1. Heating food
In microwave oven when you placing food, electromagnetic waves oscillate within
the oven at a frequency of 2.45 GHz. This field interact with the food, leading to heat
generation and a rise in temperature.
2. Treating Cancer
This type of cancer therapy involves subjecting tumor tissue to localized heating
without damaging the healthy tissue around it.
