Page 125 - Decision Making Applications in Modern Power Systems

90 Decision Making Applications in Modern Power Systems

The electrical engineers are aware of the importance of the power quality.
They care about it, and they research how to improve it. They see everything
that affects voltage, current, and frequency of the power that would be sup-
plied to consumers. They have made standards on power quality at all levels
of the power system, such as large generation units, distributed generation
(DG) units, transmission lines, and ultimate consumers. Nowadays, not only
the electricity generation units deal with power quality but also the consu-
mers, small generation unit owners, utility owners, industrial units, and home
appliance producers care about the same.

4.1.1 Power quality definition and standards
Power quality has different meanings from different points of view; it could
be a problem to be solved, or it is a part of the product. If it is seen from the
point of view of an electrical engineer or a power quality expert, it is a prob-
lem that should be solved; on the other hand, if it is seen by a power mar-
keter, a producer of electricity, or a consumer, it is a part of the product. On
both ends of the spectrum, power quality is an important part of the product
that should best fit the needs.
From the technical point of view, reliability, availability, and power
quality are the most important aspects of electrical power, which are some-
how interconnected. The power quality concept could be studied posterior
to having a reliable electricity source, which is available most of the time.
As these qualitative definitions are not any proper evaluation criteria for
power quality, there should be some quantitative standards to measure the
quality of the power. During the last 30 years, several standards for power
quality have been published and updated. Though the definitions are almost
the same, some details are being added to each update, or the limits are
becoming more rigorous. IEC, IEEE, ANSI, and NEMA have adapted sev-
eral standards on power quality for different aspects of the issue [4].IEC
has developed a category of standards called EMC (electromagnetic compat-
ibility) to deal with the power quality issues. Although EMC has been
adopted in the European Union as a requirement of the equipment sold in
Europe, their application in other countries varies, and few of them are used
in the United States. In the United States, there are a number of standards
developed by IEEE, ANSI, and some manufacturer companies such as
NEMA on power quality, and most of these standards are application based.
Among those the most important power quality standards are IEEE p1159
and IEEE 519 that have been revised several times and define limits of dis-
tortions for different levels of power system. An example of these defini-
tions is shown in Table 4.1 [5 7]. For detailed definitions on voltage
quality, current quality availability, etc., the provided references could be
useful [8,9].