Steps in solving power quality problems usually include interaction between the utility supply system and the customer facility. This is because power quality problems have different causes that can be traced from both the utility and the end-users. Consequently, different solutions are available in order to improve the power quality and equipment performance. The problem solving process should also consider whether the assessment involves an existing power quality problem or one that could result from a new design or from proposed alterations to the system.continue..

Voltage Swell is defined by IEEE 1159 as the increase in the RMS voltage level to 110% - 180% of nominal, at the power frequency for durations of ½ cycle to one (1) minute. It is classified as a short duration voltage variation phenomena, which is one of the general categories of power quality problems mentioned in the second post of the power quality basics series of this site. Voltage swell is basically the opposite of voltage sag or dip..continue..

Interruptions are classified by IEEE 1159 into either a short-duration or a long-duration variation. However, the term “interruption” is often used to refer to short-duration interruption, while the latter is preceded by the word “sustained” to indicate a long-duration. They are measured and described by their duration since the voltage magnitude is always less than 10% of nominal..continue..

Ambiguous Power Quality Terms have proliferated in the power quality community today. Generally, these confusing terms are created by marketers, using many colorful phrases to attract and entice potential customers to buy their products. Unfortunately, many of these terms can’t be used for technical definitions. As a result, the Institute of Electrical and Electronics Engineers (IEEE) has discouraged the use of ambiguous terms in order to avoid and prevent confusion..continue..

In this Surge Arrester Selection Guide, an overview of the processes and criteria are given. This post is not intended to be an all encompassing reference but only as a review of the basic steps necessary to choose the appropriate surge arrester for a particular application.  In addition, a detailed input from other sources such as the manufacturer should be obtained..continue..

The Load Profile is basically a graph showing how the load demand changes with respect to time. It is the subsequent step after choosing the critical and essential loads for uninterrupted power protection. Through the load profile, the design load and energy demand values, which are prerequisites for UPS Sizing calculation, can be derived.continue..

Voltage Unbalance (or Imbalance) is defined by IEEE as the ratio of the negative or zero sequence component to the positive sequence component. In simple terms, it is a voltage variation in a power system in which the voltage magnitudes or the phase angle differences between them are not equal. It follows that this power quality problem affects only polyphase systems (e.g. three-phase).
Voltages are rarely exactly balanced between phases. However, when voltage unbalance becomes excessive, it can create problems for polyphase motors and other loads. Moreover, adjustable speed drives (ASD) can be even more sensitive than standard motors..continue..

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