The Power Quality Evaluation Procedure

Power quality problems encompass a wide range of different phenomena, as described in Chapter 2 (Terms and Definitions). Each of these phenomena may have a variety of different causes and different solutions that can be used to improve the power quality and equipment performance. However, it is useful to look at the general steps that are associated with investigating many of these problems, especially if the steps can involve interaction between the utility supply system and the customer facility. Figure 1.2 gives some general steps that are often required in a power quality investigation, along with the major considerations that must be addressed at each step. 

Figure 1.2 Basic steps involved in a power quality evaluation.

The general procedure must also consider whether the evaluation involves an existing power quality problem or one that could result from a new design or from proposed changes to the system. Measurements will play an important role for almost any power quality concern. This is the primary method of characterizing the problem or the existing system that is being evaluated. When performing the measurements, it is important to record impacts of the power quality variations at the same time so that problems can be correlated with possible causes. 

Solutions need to be evaluated using a system perspective, and both the economics and the technical limitations must be considered. Possible solutions are identified at all levels of the system from utility supply to the end-use equipment being affected. Solutions that are not technically viable get thrown out, and the rest of the alternatives are compared on an economic basis. The optimum solution will depend on the type of problem, the number of end users being impacted, and the possible solutions. 

The overall procedure is introduced here to provide a framework for the more detailed technical information and procedures that are described in each chapter of this book. The relative role of simulations and measurements for evaluating power quality problems is described separately for each type of power quality phenomenon. The available solutions and the economics of these solutions are also addressed in the individual chapters.