Consulting-Specifying Engineer - September 2008 - (Page 34)

\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\ gain experience with the systems. It is also imperative that periodic testing and/or re-commissioning of an existing electrical system be performed to help ensure that it continues to operate per the design intent. Electrical commissioning The following is an example of how these phases were implemented to successfully commission the electrical systems for a critical data center in North Carolina. The owner’s pre-design requirement was for a data center facility that had a concurrently maintainable infrastructure with fault-tolerant critical systems. During this phase the owner also determined that all critical electrical systems would be factory tested and then validated through on-site testing. Because the commissioning agent was involved in the pre-design discussions, he was aware of the owner’s expectations. The data center’s design was based on an isolated redundant-type system with a primary distribution system for each section of the data center, and a redundant distribution system to back up the primary systems. Many crucial decisions made during the design phase impacted the operation of the facility and commissioning. For example, the owner preferred to have two sources of power to this facility, but only one medium-voltage source was available in the area. The client decided to spend extra money in redundant backup systems. Having knowledge of key design decisions helped the commissioning agent to develop the validation testing procedures. Commissioning factors also affected the design of the distribution system. The owner required that a portion of the data center be live, serving critical load before the entire facility could be completed. The redundant systems were installed first in a section of the existing building, and the existing service was used to temporarily serve the data center until the new service and UPS plant were constructed. Once the new primary systems were installed, they had to be tested and commissioned around a live data center. Developing the commissioning plan early in the project was vital in providing guidance on how to design and build the facility so that the later phases of construction could be tested and validated without affecting the portion that was already online. During the construction phase, all parties reviewed equipment submittals, and all critical electrical equipment was factory witness tested. Due to the complexity of the electrical systems, the manufacturer developed a simulator for testing. Through the use of the simulator, various failure scenarios were tested and the control sequence was modified so that the system operated per the requirements of the owner. Commissioning procedures and checklists were written. In addition, the arc flash analysis and coordination study were reviewed, and all protection device trip settings were verified. The operational phase was split into multiple sections because of the phased construction. In each phase of construction, the individual pieces of equipment were tested; the discrete systems required to bring that particular phase online were then tested. Once all phases of construction were completed, the entire facility was turned over for integrated systems testing, where a “black start” test was conducted with multiple failure scenarios (loss of generator, loss of primary backup system, UPS failure, etc.). Problems did occur in each phase of testing (defective breakers, interaction of systems during a failure, coordination issues with inrush, etc.). All of these problems were corrected and retested until the system operated per the design intent. The month after the facility was fully commissioned, the owner started a worldwide migration to the new facility. Halfway through the migration, a snake crawled across two phases of a 25 kV utility service switch and caused a fault that interrupted service to the facility. During the utility power outage, one of the standby systems tripped and went offline. The electrical system reacted properly and transferred the critical load to the redundant standby power system. Because the electrical system was commissioned, it operated as designed and the owner never lost power to the critical load. The owner estimated that the cost to recover from losing power to the critical load during the migration would have been $5 million. Two key tasks of commissioning electrical systems are: • Defining the value to the client • Becoming involved early in the design process. The more complex and critical the electrical system becomes and the greater the exposure to risk involved with loss of power, the more crucial it is to commission the system and verify that it will operate as designed. Kutsmeda is engineering design principal/assistant electrical chief with KlingStubbins, Philadelphia. For more than 15 years, he has been responsible for the engineering, design, and commissioning of electrical power and lighting distribution systems. His project experience includes 7x24 mission critical facilities, highly specialized research and development buildings, and large-scale technology projects. \\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\ Testing references References for inspecting and testing electrical distribution equipment are: • ANSI C37.50—Low-Voltage AC Power Circuit Breakers Used in Enclosures—Test Procedures • IEEE 450—Recommended Practice for Maintenance, Testing and Replacement of Vented Lead Acid Batteries for Stationary Applications • IEEE 1188—Recommended Practice for Maintenance, Testing and Replacement of Valve Regulated Lead Acid Batteries for Stationary Applications • NEMA AB4—Guidelines for Inspection and Preventive Maintenance of Molded Case Circuit Breakers Used in Commercial and Industrial Applications • NETA ATS—Acceptance Testing Specifications for Electrical Power Distribution Equipment and Systems • NFPA 70B—Recommended Practice for Electrical Equipment Maintenance • NFPA 70C—National Electrical Code • NFPA 70E—Standard for Electrical Safety in the Workplace • NFPA 101—Life Safety Code • NFPA 110—Standard for Emergency and Standby Power Systems • NFPA 111—Standard for Stored Energy Emergency and Standby Power Systems • OSHA 34 Consulting-Specifying Engineer • SEPTEMBER 2008

Table of Contents Feed for the Digital Edition of Consulting-Specifying Engineer - September 2008

Consulting-Specifying Engineer - September 2008 Contents Viewpoint Letters News M/E�Roundtable Selecting Appropriate Egress Strategies Commissioning On-Site Electrical Systems Mentoring Control Engineers and Technicians Casting Call for Cx Case Study New Products Equipment Lifecycles Advertiser Index Green Space

Consulting-Specifying Engineer - September 2008

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