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Power Quality Information

What is the difference between power reliability and power quality?

Most utilities and the Federal Energy Regulatory Commission (FERC) measure power system reliability in terms of extended outages experienced on a power line. Disturbances lasting less than a minute are typically not counted as outages. Sensitive electronic equipment, widely used today in factories, offices, warehouses and residences, can be affected by disturbances lasting ¼ second or less. Power quality deals with the area of short duration disturbances.

Can I completely eliminate the chance of power quality events?

Power disturbances occur because of lightning strikes, storms, accidents, equipment failure and trees falling on utility lines. Such events can never be eliminated, even on the most reliable utility systems. Utility protective equipment normally operates to isolate the section of the line where a fault occurs, and very quickly restores power under all except the most catastrophic situations. As a result, most power disturbances are of very short duration, typically less than ¼ second. Based on an extensive study by the Electric Power Research Institute, a consortium of over 300 utilities from around the world, less than 3% of power disturbances represent power outages. The rest are short duration disturbances.

How can I minimize my power quality events?

The i-Grid only records power disturbances that occur on your power line. Based on the type and frequency of events measured, and on the cost of downtime at your facility, one can then decide on a power solution that meets your process and budget requirements. Visit Rockwell Automation for further information on power quality and reliability solutions.

How frequently do power disturbances occur?

This can vary widely based on type of utility service, geographic region, presence of disturbing loads, and natural factors such as storms, lightning and ice storms. The Electric Power Research Institute reports in their Distribution Power Quality study that typical industrial sub-stations on radial distribution feeds experience approximately 25 power disturbances (events) per year that could potentially impact a customer's process. Only 3% of these disturbances were seen to be extended outages. Large power consumers connected to high voltage utility grids (>110,000 volts) will typically experience higher reliability levels, experiencing virtually no outages. However, short duration disturbances cannot completely be eliminated.

What impact do these power disturbances have on equipment and processes?

It is well known that for computer systems and data networks, power disturbances can cause system lock-up, data loss and significant downtime. Even in the industrial arena, manufacturing today invariably has automation, computers and programmable controllers integrated into the process. Significant costs are incurred if the process goes down because of a power disturbance. These include scrap material costs, clean up time, long restart time, additional labor costs and opportunity costs. In some sectors such as semiconductor manufacturing, cost of downtime can exceed $1 million per event. The pain of lost productivity is however universally felt across all manufacturers and businesses.