18-03-2014, 12:35 PM
Electrical Power Systems Quality, Second Edition
Introduction
Both electric utilities and end users of electric power are becoming
increasingly concerned about the quality of electric power. The term
power quality has become one of the most prolific buzzwords in the
power industry since the late 1980s. It is an umbrella concept for a mul-
titude of individual types of power system disturbances. The issues
that fall under this umbrella are not necessarily new. What is new is
that engineers are now attempting to deal with these issues using a
system approach rather than handling them as individual problems.
There are four major reasons for the increased concern:
Why Are We Concerned about Power
Quality?
The ultimate reason that we are interested in power quality is eco-
nomic value. There are economic impacts on utilities, their customers,
and suppliers of load equipment.
The quality of power can have a direct economic impact on many
industrial consumers. There has recently been a great emphasis on
revitalizing industry with more automation and more modern equip-
ment. This usually means electronically controlled, energy-efficient
equipment that is often much more sensitive to deviations in the sup-
ply voltage than were its electromechanical predecessors.
Need for a Consistent Vocabulary
The term power quality is applied to a wide variety of electromagnetic
phenomena on the power system. The increasing application of elec-
tronic equipment and distributed generation has heightened the inter-
est in power quality in recent years, and this has been accompanied by
the development of a special terminology to describe the phenomena.
Unfortunately, this terminology has not been consistent across differ-
ent segments of the industry. This has caused a considerable amount of
confusion as both vendors and end users have struggled to understand
why electrical equipment is not working as expected. Likewise, it is
confusing to wade through the vendor jargon and differentiate between
a myriad of proposed solutions.
Many ambiguous words have been used that have multiple or
unclear meanings. For example, surge is used to describe a wide vari-
ety of disturbances that cause equipment failures or misoperation. A
surge suppressor can suppress some of these but will have absolutely
no effect on others. Terms like glitch and blink that have no technical
meaning at all have crept into the vocabulary. Unscrupulous marketers
take advantage of the ignorance of the general public, selling over-
priced gadgets with near-miraculous claims for improving the power
quality. Of course, this all comes with a money-back guarantee.
Readers can protect themselves by obtaining a better understanding of
power quality vocabulary and insisting on technical explanations of
how a gadget works. Our basic rule: If they won’t tell you what is in the
box and how it works, don’t buy it!