UFC 3 -520-01
June 10, 2002
POWER QUALITY DESIGN .
A facility should be designed to withstand the most likely power quality
problems, commensurate with the importance of the facility's mission. For critical
equipment, include power quality features at the design stage to ensure that system
reliability goals are maintained. Acceptable power quality is not achieved by a single
system design feature. Evaluate the following elements as part of the facility design:
Appropriate grounding, including cons iderations of unbalanced and nonlinear loads.
Voltage sag and power interruption impacts.
Effect of switching transients, particularly if the local utility operates capacitors
electrically near the facility.
Power factor correction requirements.
Voltage variations associated with motor starting and other transients.
Degree of unbalanced voltage for three phase systems supplying single phase
Consider the requirement for continued reliable facility operation, t he impact
of electrical system-related power disruptions, the types of power disturbances that can
occur, and the various cost -effective methods of ensuring power quality.
The addition of power quality design equipment often has an iterative effe ct
on the electrical system design. For example, the addition of power conditioners affects
the system voltage drop to downstream devices. Not all power quality issues can be
addressed during the system design. Monitor power system quality at the service
entrance to determine if additional design measures will be needed.
Each power quality issue can require a different type of design solution; a
single standardized design approach will not satisfy all power quality issues. Table 12-2
provides a summary of typical design approaches to power quality problems.