Keith Lane, P.E., Vice President - Engineering, SASCO, Seattle
Articles
Sizing Neutrals for Transformers
K-rated transformers are typically used where anticipated loads include nonlinear power supplies. They don't remove harmonic distortion from the system. Rather, they handle the added current and heating effects resulting from nonlinear loads without damage. Underwriters Laboratories has established ratings of 1, 4, 9, 13, 20, 30, 40 and 50 as standard K-factor ratings.
Location Location Location
That a majority of outages in critical environments are caused by disruptions between the uninterruptible power supply (UPS) and the critical load has been indicated by a number of studies. Other researchers have noted that 70% to 80% of the outages in critical environments are caused by human error (For more information, visit the Uptime Institute at www.uptimeinstitute.com ). A means of transferring between sources of power within the confines of the Computer Business Manufacturers Assn. (CBEMA) or ITI curve is essential in critical environments that require high levels of site availability. A static transfer switch (STS) will permit very fast transfer between power sources and can allow the system to survive a single failure or a single human error.
Coordinated Protection for Critical Environments
There's no doubt that a sudden power failure can have a dramatic effect on business, especially in a facility with critical operations. Isolating a fault condition to the smallest area possible is essential in providing the most reliable electrical system with maximum uptime for the facility. But expensive electronic distribution protection equipment might not be worth the extra cost unless a p...