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Training Session on Energy
Equipment
Electrical Systems
Presentation to
Energy Efficiency Guide for Industry in Asia
Chapter 1
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© UNEP GERIAP
Training Agenda: Electricity
Introduction
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© UNEP 2005
Electricity
General Electricity Scenario
• Development can be measured by a
nation’s electricity consumption
• Electricity usage is divided into:
a) Industrial
b) Commercial and residential
c) Agriculture and irrigation
• Electricity is one of the most
important inputs for the industrial
sector
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© UNEP 2005
Electricity
General Electricity Scenario
•
Electrification in developing countries will
reach 78% of the population by 2030 (World
Energy Outlook)
•
Electricity supply must increase by 1,000
tWh to satisfy the world’s electricity
demand by the year 2030 (World Energy
Outlook)
•
The world’s poorest and remote will gain
more electricity access (World Energy
Outlook)
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© UNEP 2005
Electricity
General Electricity Scenario
• How can the challenge of the growing
gap between electricity demand and
supply be solved?
a) Renovation and modernization of plants,
transmission and distribution systems
b) Demand side management
c) Awareness raising among energy users
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© UNEP 2005
Electricity
Generation & Distribution
• Most of the world's electricity is generated
using non-renewable energy sources such
as fossil fuels (coal, gas and oil) and
radioactive substances such as uranium
• Renewable
energy technologies is widely
researched to
make it better
and cheaper
World electricity
generation by energy
Renewable 21%
Nuclear 16%
Fossil fuels 63%
Figure: World electricity generation 6
Source: EIA
© UNEP 2005
Electricity
Generation & Distribution
• Electricity is generally generated by AC
generators known as “alternators” in
thermal, hydro or nuclear plants
• Electricity is typically generated at 9-13 KV
and the power generated is in the range of
67.5 MW, 110 MW, 220 MW, 500 MW
• Generated power is transmitted to the user
end through a transmission & distribution
network
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© UNEP 2005
Electricity
Generation & Distribution
Transmission
system
Power plant
Generator
GT
10.6 KV
Distribution system
220 KV
Distribution
Step down
transformer
Figure: Single line diagram of generation and transmission system
•
All power stations have generating transformers (GTs) that step up the voltage level 132400 KV
•
Conversely, sub-stations have step-down
transformers to reduce voltage before
distribution
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Electricity
Phase of Electricity
A single phase AC circuit:
• Has two wires connected
to the electricity source
• The direction of the
current changes many
times per second
Figure: 3-phases of electric system
Source: Wikipedia
Three phase systems:
• Have 3 waveforms that are that are 2/3π radians
(120 degrees,1/3 of a cycle) offset in time
• The cycle in the figure above will repeat itself
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50-60 times per second
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Electricity
Active and Reactive Power
•
Active power (kW) is the real power used by any
load to perform a task
•
Reactive power (kVAR) is virtual in nature and
decides the load/demand on an electrical system
•
The utility has to pay for the total power (kVA)
kVA =  (KW)2 + (KVAR)2
Figure: Representation of power triangle
Source: OIT
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Electricity
Power Factor Correlation
• Power factor is the
ratio of active power
(kW) to the apparent
power (kVA) =
Cosine of the angle Figure: Power factor of electric circuit
• The undesirable
component (kVAR)
demand should be
as low as possible
for the same kW
output
Figure: Capacitor as kVAR generator
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© UNEP 2005
Electricity
Improving Power Factor
• Correction
capacitors act as
reactive power
generators and
accomplish kW of
work
• This reduces the
amount of total
power that has to
be generated by the
utilities
Figure: Fixed capacitor banks
Source: Ecatalog
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© UNEP 2005
Electricity
Improving Power Factor
Advantages with capacitor addition:
•
Reactive component of the network is reduced
and also the total current in the system from
the source end
•
I2R power losses are reduced in the system
because of reduction in current.
•
Voltage level at the load end is increased
•
kVA loading on the source generators as also
on the transformers and lines up to the
capacitors reduces giving capacity relief 13
© UNEP 2005
Electricity
Improving Power Factor
Cost benefits of power factor improvement:
•
Reduced kVA (maximum demand) charges in
utility bill
•
Reduced distribution losses (kWH) within the
plant network
•
Better voltage at motor terminals and improved
performance of motors
•
A high power factor eliminates penalty charges
imposed when operating with a low power
factor
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© UNEP 2005
Electricity
Electrical Load Management
• A load curve is
useful for integrated
load management
by predicting
patterns of drawl,
peaks and valleys in
demand
KVA
• The goal of peak load management is to
reduce the maximum electricity demand to
lower the electricity costs
Hours
Figure: Daily load curve of an 15
engineering industry
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Electricity
Electricity Billing Mechanism
• Maximum Demand Charges
• Energy Charges
• Fuel cost adjustment charges
• Electricity duty charges
• Meter rentals
• Lighting and fan power consumption
• Time Of Day (TOD) rates
• Penalty for exceeding contract demand
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© UNEP 2005
Electricity
1) Shifting Non-Critical and
Non-Continuous Process
Loads to Off-Peak time
Rescheduling of large electric loads and equipment
operations in different shifts, these can be planned and
implemented to minimize the simultaneous maximum
demand.
2) Shedding of NonEssential Loads during
Peak Time
It is possible to install direct demand monitoring systems,
which will switch off non-essential loads when a preset
demand is reached.
3) Operating In-House
Generation or Diesel
Generator (DG) Sets during
Peak Time
Connect the DG sets for durations when demand reaches
the peak value in order to reduce the load demand to a
considerable extent and minimize the demand charges.
4) Operating Air
Conditioning units during
off-peak times and utilizing
cool thermal storage
Reduce the maximum demand by building up storage
capacity of products/ materials, water, chilled water / hot
water, using electricity during off peak periods.
5) Installation of Power
Factor Correction
Equipments
The maximum demand can also be reduced at the plant
level by using capacitor banks and maintaining the
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optimum power factor.
Table: Peak load management strategies
Peak Load Management Strategies
© UNEP 2005
Electricity
Peak Load Management Strategies
•
The demand varies
from time to time
•
Maximum demand is
the time integrated
demand over the
predefined
recording cycle
•
Trend analysis can
help identify key
areas for electricity
cost reduction
Figure: Typical demand curve 18
© UNEP 2005
Electricity
Transformer
•
A static electrical device that
transforms electrical energy
from one voltage level to
another
•
Consists of two or more coils
that are electrically insulated
but linked magnetically
•
Figure: 3 phase core&coil
assembly of a transformer
Source: Kuhlman
The number of turns on the 2nd coil
(connected to the load) to the turns on the 1st
coil (connected to the power source) is the
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turn’s ratio
© UNEP 2005
Electricity
Types of transformer
Table: Classification of transformers
Types
Criteria
Based
voltage
on
Input
Step Up
Transforms LV to HV
Step Down
Transforms HV to LV
Power Transformer
Located at Power Stations to Step up the voltage
& handles large power. Typical voltage ratings
are 400 kV, 220kV, 132KV, 66 kV, 33kV etc.
Distribution
Transformer
Located at Sub-Stations of a distribution network
and handles low power. Typical voltage ratings
are 11kV, 6.6 kV, 3.3 kV, 440V, 230V etc.
Instrument
Transformer
Used for measuring high voltage and current in
measuring instruments
Outdoor
Located outside on a concrete structure or iron
pole structure
Indoor
Located inside a shed on concrete structure
Three Phase
Input & output supply are of three phases (R/Y/B)
with or without neutral
Single Phase
Input & output supply are of single phase
Based on Operation
Based on Location
Based
Connection
on
Remark
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© UNEP 2005
Electricity
Transformer Losses & Efficiency
PTOTAL = PNO-LOAD+ (% Load/100)2 x PLOAD
PTOTAL = PNO-LOAD+ (Load KVA/Rated KVA)2 x PLOAD
Figure: Transformer loss vs. % loading
• The transformer losses are due to constant
and variable losses
• The best efficiency occurs at the load 21
where constant loss and variable loss ©are
UNEP 2005
Training Session on Energy
Equipment

Electrical Systems
THANK YOU
FOR YOUR ATTENTION
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© UNEP GERIAP