Central Campus Utility Master Plan
University of Houston
Electrical Distribution System Study Phase 1 & 2:
Shah Smith & Associates, Inc. provided an evaluation for the University of Houston Central Campus electrical distribution system. UH distributes power to the campus at 12.47 kV from the Central Plant. Nine pairs of parallel feeders serve the campus buildings with each building being served by a pair of feeders for redundancy. The Central Plant receives power from a utility substation, by way of three 12.47 kV circuits.
This study investigated the existing campus power distribution system, both in arrangement and capability to determine both operational and infrastructural changes necessary to serve future campus needs. The most cost effective solution was found to be the installation of a second electrical service for the campus. The study included a load flow analysis of the electrical distribution system.
Two other options were investigated to meet the future needs of the campus. The first included renovating the existing electrical service to expand the campus feeder capacity. However, this was found to be infeasible as it would require too many interruptions to the existing campus and would require replacing far too many components that are otherwise perfectly functional. The third option investigated augmented the existing central power system with additional Centerpoint-supplied power at future buildings, but this was found to be infeasible due to the expansive layout of proposed future development, the additional service cost charged for secondary services to buildings as opposed to primary service to campus, and the restrictions that required utility easements would place on the campus’ future growth.
In August 2010, a cable fault on one of the incoming feeders occurred. The protective relaying scheme for the electrical system was not properly coordinated, the fault could not be isolated, and the entire electrical system tripped. SSA was tasked with three items to resolve the problem: Electrical System Study, provide a short circuit and relay coordination study for the entire campus, review and make recommendations on the campus electrical distribution system to provide more reliability, and review the existing campus electrical system testing procedures and recommend changes.
Chilled Water, Steam, and Condensate Distribution Study:
UH was experiencing significant growth around campus. One of the issues associated with campus expansion was the ability of the chilled water, steam, and condensate systems to meet the new capacity requirements. Accordingly, the Central Plant was being upgraded to meet the new campus utility demands and the distribution system needed to be analyzed for deficiencies. This study was conducted to develop computer hydraulic models of the chilled water, steam, and condensate systems to identify limitations in distribution systems and to determine if any modifications were required.
The modeling and evaluation of the steam and condensate systems showed that there was adequate capacity for the foreseeable future. The only concern with these systems was the life of the piping. Steam and condensate piping is more subject to internal corrosion than closed loop water systems. UH has implemented a systematic plan for replacing steam and condensate piping.
The chilled water model of the campus distribution showed that about three-fourths of the buildings on campus had a negative available ΔP. Negative ΔP can be a problem because it must be overcome by the building pumps, which are often not sized for this condition and it creates the potential for chilled water from the return to mix with the supply, which wastes energy. Additionally, as new buildings are built, the available ΔP becomes even more negative.
The 30 inches cross connect chilled water lines that SSA recommended, which were installed, provided significant improvement in the chilled water distribution system. Some additional improvements can be made by upsizing existing lines as the existing lines reach the end of their useful lives and are replaced.
To address life expectancy of the closed loop chilled water piping, a non-destructive evaluation of the piping was planned, which will measure the pipe wall thicknesses throughout the system. Then, based on the age of the pipe and its original thickness, a plan for replacing the piping will be developed.