Consulting-Specifying Engineer - March 2009 - (Page PP2) ❯❯ PURE POWER // SPRING 2009 2 paralleled generator COVER STORY PARALLELED GENERATOR SYSTEM CONSIDERATIONS Learn how to ensure that standby power systems will work well when called upon without damaging the equipment they are meant to protect. By Keith Lane, PE, RCDD/NTS Specialist, LEED AP Lane Coburn & Associates LLC, Seattle MW generators are paralleled to achieve the (N) load, six aralleled generator systems provide many advangenerators would be paralleled together to achieve N+1. If tages, especially for large, power-dense applicathe actual build-out and usage of the data center was only tions. Designing the most efficient and reliable 80% of the design load, the total load would be 8 MW. Four, system for a specific application requires a solid 2 MW generators could supply the load, so with six total understanding of the options available. generators, the system would achieve N+2 redundancy. InThis article summarizes some of the key points and design dependent strings of generator backup systems would not be criteria involved in designing a paralleled generator system able to handle an outage of two generators without affecting for capacity, redundancy, and reliability in critical operations. critical loads, even at 80% of the design load. It also covers some of the compatibility issues related to critiDepending on the configuration of the electrical districal electrical distribution systems that include both generabution system, a paralleled system can achieve the required tors and UPS systems. redundancy using fewer total generators than a system with Critical installations can be classified using a tiered individual strings of electrical components. system, with Tier 1 being the most basic, offering the least Load-bank testing the generators is much simpler. An amount of redundancy and uptime, and Tier IV being the most complex and expensive, offering the most uptime and reliability. With Figure 1: A six generator (5+1) configuration (closed-transition paralleling gear with a single the emergence of Tier III and Tier IV utility feeder) is shown. Utility and generators are at 12,470 V. data centers in the 1990s and the early 2000s, engineers began specifying UTILITY A FUTURE FEEDER UTILITY B FEEDER paralleled generator systems to increase 'B-SE' UTILITY SWGR 'A-SE' UTILITY SWGR the redundancy of the generators to B-SE 1200/3 N.C. N+1 and greater, as required for these SPACE higher-tiered data centers (for the TIE/B-SE 1200/3 N.O. Uptime Institute’s definition of Tier SPACE SPACE III and Tier IV data centers, go 1200/3 1200/3 N.C. N.C. to www.uptimeinstitute.org). 1200/3 1200/3 Although a design also can achieve N.C. N.C. the required redundancy from the gen1200/3 1200/3 N.C. N.C. erator through standard automatic-trans1200/3 1200/3 N.C. N.C. fer switches (ATSs) and downstream A-GP B-GP interweaving of dual cord servers, there GENERATORS 1200/3 1200/3 PRIME 1BOCKW/2250KVA N.O. N.O. STANDBY 2000KW/2500KVA are many reasons why a paralleled 12470 V 1200/3 1200/3 G2 G1 generator system may be preferred, N.D. N.O. LUGS FOR including: PORTABLE GEN. SET G3 1200/3 G4 1200/3 N.O. N.D. At less than 100% of design load, 1200/3 N.O. N.O. N.O. G6 G5 1200/3 1200/3 more than N+1 can be achieved with LOAD 'A-GP' GENERATOR PARALLELING SWITCHGEAR 'B-GP' GENERATOR PARALLELING SWITCHGEAR BANK paralleling gear. For instance, if the total data center load is 10 MW and five, 2 P www.purepowermagazine.com Source: Keith Lane http://www.uptimeinstitute.org http://www.purepowermagazine.com
For optimal viewing of this digital publication, please enable JavaScript and then refresh the page. If you would like to try to load the digital publication without using Flash Player detection, please click here.