Improving Power Quality on Distribution Lines

New standard defines emerging technology with solutions and applications


Sophisticated computer-based industrial automation equipment and a wide range of microprocessor-based information technology (IT) in offices have made power quality an increasingly critical issue for North American electric utilities. Many problems have arisen for utility customers from short-lived—but problematic—power quality on distribution lines phenomena such as voltage sag, voltage interruptions, flicker, harmonic distortion and voltage regulation issues.

Technologies exist to eliminate or substantially mitigate these problems but utilities have lacked a best-practices document to guide “custom power” programs. To address this issue, the IEEE Standards Association recently published a new standard, IEEE 1409: “Guide for Application of Power Electronics for Power Quality Improvement on Distribution Systems Rated 1 kilovolts Through 38 kV”, which provides guidelines and performance expectations for the application of power electronic-based equipment on distribution systems of power providers to improve power quality.

Although IEEE 1409 is specifically applicable to distribution-class (1 kV to 38 kV) power facilities, the technologies and practices may be useful in other applications. The standard provides definitions, descriptions of power quality phenomena, performance measurements, and application configurations, but the core of the document addresses the technologies that can be used in power quality remediation programs. They fall into two categories: Voltage sag and interruption protection devices and reactive power and harmonic compensation devices.


Dynamic Voltage Restorer (DVR)
A dynamic voltage restorer (DVR) mitigates voltage sags and interruptions on a sensitive load. Essentially a waveform synthesis device, it connects directly into the primary distribution circuit over a set of single-phase injection transformers. DVRs can be configured to inject line energy supply (LES) energy into the distribution circuit from the utility feeder. In this system configuration, when the voltage of one or more phases of the incoming supply drops below a preset threshold, the DVR injects a controlled amount of voltage into the affected phase or phases to restore the load voltage to a suitable level.

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