Electric Distribution Systems

 

General

The purpose of this report is to develop a brief analysis of the existing electric distribution systems at the Taylorsville Redwood, Jordan, South City, Miller, and Meadowbrook campuses of Salt Lake Community College. The result of this portion of the analysis will be as follows:

  • Determine current campus electric demand and energy use
  • Project future campus electric demand
  • Determine whether or not the existing electric facilities will be adequate for the future loads
  • Recommendations regarding the future electric infrastructure

This report will facilitate in providing a basis for planning, funding, and implementation for future years; however this is not a utility master plan. The report is predicated on the need to provide continued reliable service to existing campus buildings and to determine whether or not the existing infrastructure will be able to support facilities as the campus expands.

Scope of Work

This report analyzes the existing and future needs of the main electrical service to the campuses.

The key items undertaken by this study include:

  • Collect and review the existing electric energy and demand data
  • Identify service voltage, main feeder size(s)
  • Utilizing the architectural master plan data (provided by AJC), estimate future campus electric demand
  • Determine whether or not the electric service in its current state can support the projected campus growth
  • Recommendations

Analysis of campus distribution systems (primary feeders, transformers, secondary feeders, service to individual buildings, etc.) will not be included in this report. However, it should be noted that if new buildings are added, or the demand of an existing building is substantially increased, additional distribution equipment and/or individual building service equipment upgrades will be required.

Conceptual Cost Estimates

Conceptual cost estimates will not be included in this report, but are highly recommended when performing the in depth utility master plan in the future.

Existing Campus Electric Loads

Electric energy and demand data for the Taylorsville Redwood, Jordan, and South City campuses is available from the Rocky Mountain Power Energy Profiler. Billing data for the Miller Campus and the Meadowbrook Campus were provided by Salt Lake Community College. These data were analyzed as part of this study.

Load Data Summary

The following table summaries the energy and demand findings and the gross square footage of the existing buildings for each campus.

Table 3.3 - Summary of Campus Energy and Demand

Campus Highest Month Energy, kWh Demand, kW GSF W/SF
Taylorsville Redwood 1,803,522 4,319 1,117,914 3.86
Jordan 552,146 1,344 250,294 5.37
South City 443,107 1,220 346,247 3.52
Miller
(6 meters)
433,580 1,091 197,892 5.51
Meadowbrook 60,720 177 70,406 2.51

 

Future Campus Electric Loads

The electric demand for the future is estimated based on the existing electric demand plus an estimated 4 Watts per square foot of additional building space identified in the architectural master plan.

Table 3.4 - Future Campus Electric Loads

Campus Existing GSF New GSF GSF at Buildout Future Demand Estimate, kW
Taylorsville Redwood 1,117,914 225,000 1,342,914 5,219
Jordan 250,294 600,000 850,294 3,744
South City 346,247 200,000 546,247 2,020
Miller
(6 meters)
197,892 40,000 237,892 1,251
Meadowbrook 70,406 52,000 122,406 385

 

The primary feeder to each of the campuses is, or will soon be, 12.47kV. The following table shows the future estimated peak electric current that is expected in a single feeder to each campus based on historic loads and based on the projected future demand estimate (assumed power factor = 0.8):

Table 3.5 - Future Campus Peak Electric Current (Single Feeder)

  Current Conditions Projected at Build Out
Campus Peak kVA @
.8 PF
Amps @
12.47kV
Peak kVA @
.8 PF
Amps @
12.47kV
Taylorsville Redwood 5,399 250 6,524 302
Jordan 1,680 78 4,680 217
South City 1,525 71 2,525 117
Miller
(6 meters)
1,364 63 1,564 72
Meadowbrook 221 10 481 22

 

The following table shows the normal condition ampacities of the cables typically used by Rocky Mountain Power for underground distribution at 12.47kV installed in duct:

Table 3.6 - Typical Cable Ampacities (Normal Conditions)

15kV Cable Ampacity at 75% Load Factor in Duct
#2 Solid Al, 175 mil, TRXLPE 125 A
#4/0  Al, 175 mil, TRXLPE 244 A
1000 kcmil Al, 175 mil, EPR 580 A

 

Conclusions and Recommendations

Taylorsville Redwood Campus: The loads at the Taylorsville Redwood Campus would be ideally served by two dedicated 1000 kcmil underground feeders from independent substations. Each feeder could then provide adequate capacity to serve the entire campus load independent of the other feeder. This redundancy would allow for looping and increased reliability and flexibility in the distribution system operation. With a peak demand of over 5MW, the Taylorsville Redwood Campus can continue to purchase power from Rocky Mountain Power under the provisions of Schedule 8. Alternatively, a substation could be installed near the campus and delivery could be taken at high voltage under the provisions of Schedule 9. A separate analysis should be completed to determine the feasibility and payback associated with the construction of a substation. There is already a second feed for this campus with an ATO switch.

Jordan Campus: The loads at the Redwood Campus would be ideally served by two dedicated #4/0 underground feeders from independent substations. Each feeder could then provide adequate capacity to serve the entire campus load independent of the other feeder. This redundancy would allow for looping and increased reliability and flexibility in the distribution system operation. If bulk metered (at 12.47kV) from one point of delivery, the current and future loads are consistent with the provisions of Rocky Mountain Power Schedule 8. Rocky Mountain Power currently does not have a second feed available for this campus. They would need to complete and estimate for this measure if it is required. The cost would be borne by SLCC.

South City Campus: Following the improvements proposed for the Spring of 2009 the system will be served at 12.47kV. Even after the proposed expansions, it is anticipated that the South City Campus loads could be adequately served with the capacity of a #2 underground feeder. A second feeder would allow for looping and increased reliability and flexibility in the distribution system operation. If the campus continues to be bulk metered from one point of delivery, the current and future loads are consistent with the existing provisions of Rocky Mountain Power Schedule 8.

Miller Campus: The Miller Campus is currently served at 6 separate metered locations each being served under the provisions of Schedule 6. If the Rocky Mountain Power distribution assets are acquired, or a SLCC owned distribution system is installed, the entire campus could be served from a single point of delivery and bulk metered at 12.47kV. This could result in savings on the demand component of the power bill. Because of increased diversity (the individual building loads don't peak coincidentally), the overall demand would be decreased. After the proposed expansions, the maximum coincidental peak will likely exceed 1MW and service could be purchased under the provisions of Schedule 8. Even after the proposed expansions, it is anticipated that the combined loads could be adequately served with the capacity of a #2 underground feeder. Rocky Mountain Power also indicates that, if the meters are in close proximity to each other, a totalizing meter could be used to allow the loads to be metered together.

Meadowbrook Campus: Even after the proposed expansions, it is anticipated that the Meadowbrook Campus loads could be adequately served with the capacity of a #2 underground feeder. The demand at Meadowbrook will not exceed 1MW and the existing provisions of Schedule 6 will apply. A study should be conducted to determine why the power factor is excessively low. The addition of power factor correction capacitors will improve the low power factor and avoid the penalty currently being assessed each month by Rocky Mountain Power.