Designing electrical systems for higher education

06/10/2013


Figure 4: This diagram illustrates a sparing transformer system, which uses busway connections to single-ended unit-substations and is an alternative to the double-ended substation concept. Courtesy: Affiliated Engineers Inc.Backup systems

Reasons to provide backup power systems at university buildings stem from various code requirements for emergency and standby systems, as well as programmatic requirements for optional user-specified sensitive equipment. Generator systems, storage battery systems, and UPS systems are typical choices for universities to fulfill these special power requirements. The need for a generator system may arise from the total allocated capacity of the emergency, standby, and optional standby loads. Depending on the building type, the emergency loads are typically the smaller load, where the standby loads constitute the larger balance and may tip the scale toward the generator selection. Also, standby loads include a large component of motor loads, better handled by a generator system versus battery storage systems. When a generator is then selected, its capacity selection becomes a controversial topic in terms of determining what other optional standby loads will need to be served. Generators are mostly suited for larger buildings where the standby and optional loads add up, such as high-rise buildings and buildings with high-tech requirements, such as data centers. Smaller buildings with minimum emergency requirements can rely on battery systems (centralized or unitized) for the backup source. 

UPS systems are frequently employed in data centers and information technology (IT) equipment, and universities may need to determine which UPS system configuration is the most appropriate to install. For example, for the distributed technology equipment located in a typical floor of a facility, a choice can be made between individual rack-mounted UPS systems versus a centralized UPS system distributed to every IT closet. A centralized UPS system, with a wrap-around maintenance bypass component, may reduce maintenance calls, and may prove cost effective in a larger facility. Also, some researchers may request uninterruptible power for sensitive experiments, which similarly can be dealt with by a point-of-use UPS or a central system. 

Figure 5: This diagram illustrates a primary selective loop feeder distribution system at a Midwestern university campus. The loop is created by outdoor sectionalizing switches and point-of-use services derived via pad-mounted transformers with integral sAnother typical approach is to handle the optional standby loads as a separate system that will seldom be needed because, depending on the campus infrastructure, most outage times are brief in duration, but may need to be planned for as catastrophic events. In disaster planning, creating a connection point for a portable generating system may prove prudent, investing only in the initial infrastructure to have the ability to provide service to optional systems, such as refrigerators housing sensitive research samples. For these portable units, universities would typically have a rental agreement with a generator supplier and upon the warning of an approaching storm, for example, they could install the portable unit as a safety precaution. It is also common to provide this type of portable system provision in a central university building (i.e., Student Union), which can become a campus shelter for disaster planning and have power for normal business operations during the event (food preparation, student services). With this initial pre-investment, provisions also can be made to install a future permanent generator at this location. 



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