Print this page Overview & Energy Optimization of Power Distribution Transformers
A. Bhatia, B.E.
Course Outline
Distribution transformers
functions to step-up & step-down voltage in transporting power economically
from the power station to the final customer. Practical power transformers,
although highly efficient, are not perfect devices. Transformer losses in power
distribution networks can exceed 3% of the total electrical power generated
and are estimated to total 140 billion kilowatt-hours (kWh) per year in the
U.S.
This 4-hour course provides an overview of transformers and summarizes the key
energy conservation measures pertaining to selection, application and operation
of power transformers. The theoretical equations are kept minimum and the basic
aspects are discussed wherever deemed fit.
This course includes a multiple-choice quiz at the end, which is designed to
enhance the understanding of the course materials.
Learning Objective
Upon completing the course, you will:
- Understand the transformer action;
- Know the transformer terminology and components;
- Understand relationship between turn ratio, voltage ratio and current ratio;
- Identify the schematic symbols;
- Differentiate between step-up, step-down, and isolation transformers;
- Understand the concept of coefficient of coupling, exciting current and impedance matching;
- Know the three phase transformer connections;
- Know various types of transformers;
- Be able to define the parameters affecting selection and rating of transformers;
- Understand the transformer efficiency, load and no-load losses;
- Be able to apply the energy conservation measures during design, application & operation; and
- Be able to perform
economic evaluation.
This course is aimed at students, electrical & control engineers, energy auditors, O & M professionals, contractors, estimators, facility managers and general audience.
Course Introduction
Losses in electricity
supply systems depend on the voltage level. These are minimized by transmitting
electricity at as high a voltage as possible, consistent with demand load levels.
Transformer is an electrical device that transfers AC energy from one circuit
to another by magnetic coupling of the primary and secondary windings. This
is accomplished through mutual inductance (M). To reduce the voltage to the
desirable level, distribution transformers do consume a small portion of the
electricity in a permanent manner. The resulting standby power losses account
for up to 2% of the total electricity production.
In the past there was little concern for lowering losses in transformers. This
was mainly due to the fact that when compared to motors and other electrical
devices, transformers were considered to be very efficient. In recent years,
however, there has been a growing concern for energy conservation and for the
total operating costs of transformers. Furthermore, under the Department of
Energy, as a requirement of the Energy Policy Act of 1992, studies are under
way to determine if significant energy savings would merit setting loss goals
for a wide range of transformers.
This course attempts to provide a basic overview of transformers with some emphasis
on the transformer losses and energy conservation opportunities.
Course Content
The course content is in a PDF file Overview & Energy Optimization of Power Distribution Transformers. You need to open or download this document to study this course.
Course Summary
All transformers
operate on the principal of magnetic induction where an AC voltage applied to
the primary windings induces voltage in the secondary winding. Power transformers
are very efficient, with losses of less than 0.5% in large units. Smaller units
have efficiencies of 97% or above. It is estimated that on average transformer
losses in power distribution networks can exceed 3% of the total electrical
power generated.
The energy losses in electricity transformers fall into two components: no-load
losses or iron losses (resulting from energizing the iron core; this phenomenon
occurs 24 hours x 7 days, over the lifetime of the transformer, 30 years in
average) and load losses (arising when providing power to a user, from the resistance
of the coils when the transformer is in use, and for eddy currents due to stray
flux). Transformers may lose 1 to 2% of energy transformed as heat when they
are lightly loaded.
Technical solutions exist to reduce transformer losses by 75% at minimum (when
replacing with modern transformers) or even by 90% (when replacing transformers
over 30 years old). Energy-efficiency can be improved with better transformer
design i.e. selecting better, lower-core-loss steels; reducing flux density
in a specific core by increasing the core size; increasing conductor cross-section
to reduce current density; good balancing between the relative quantities of
iron and copper in the core and coils; amorphous iron transformers and so on...
Most distribution
and general purpose transformers are currently purchased on a first cost basis
without regard for losses or the total cost of ownership. Distribution transformers
present a range of energy efficiency. Promoting the most energy efficient transformer
technology, when replacing old equipment, can generate significant amount of
energy savings on attractive paybacks.
Quiz
Once you finish studying the above course content, you need to take a quiz to obtain the PDH credits.
DISCLAIMER: The materials contained in the online course are not intended as a representation or warranty on the part of PDH Center or any other person/organization named herein. The materials are for general information only. They are not a substitute for competent professional advice. Application of this information to a specific project should be reviewed by a registered architect and/or professional engineer/surveyor. Anyone making use of the information set forth herein does so at their own risk and assumes any and all resulting liability arising therefrom.
