Sports, entertainment venues: Electrical and power systems
Participants (left to right):
Keith Cooper, PE, President, McClure Engineering, St. Louis
Douglas H. Evans, PE, FSFPE, Fire Protection Engineer, Clark County, Nevada
Bill Larwood, PE, LEED AP, Senior Vice President/Project Principal, Syska Hennessey Group, Los Angeles
Kevin Lewis, PE, LEED AP BD+C, Vice President, Henderson Engineers, Lenexa, Kansas
Bruce McKinlay, Principal, Arup, Los Angeles
CSE: Describe some recent electrical/power system challenges you encountered when designing a new building or updating an existing building.
Lewis: As part of a press box renovation, we were asked to reuse the existing 1600 A switchboard. At first this was not expected to be a problem. However, as the design progressed, electrical loads such as kitchen equipment, AV equipment, and sports lighting were added to the project that were not originally anticipated. Ultimately, we were able to reuse the existing board, but not without replacing the main circuit breaker to be rated for 100% capacity and also telling the owner that some of the equipment on its “wish list” could not be accommodated without increasing the service size.
McKinlay: With the recent power failure at the Super Bowl, it is very apparent how important resilient and redundant power systems are. The challenges are designing electrical service and switchgear equipment without a single point of failure and also with a robustness that can accommodate varying power demands. This costs money and space, and some utility infrastructure does not offer redundant services so standby power systems are necessary.
CSE: Describe a recent project in which you specified backup, standby, or emergency power in such a facility.
Cooper: Cost seems to be the biggest challenge from project to project. The lists of “what we have to back up,” “what we would like to back up,” and “what we might want to back up some day” usually are at odds with the project budget. This normally leads to bid alternates, which can become confusing due to the effects each alternate has on where equipment is fed from, potential equipment voltage changes, how the one-line diagram changes, and the size of the generator(s). One of the most important parts of the process becomes creation of a final construction set of drawings that accurately reflect the work for the accepted alternates while removing work that will not be part of the to-be-built construction.
Lewis: We were asked to provide a standby generator for backup power as part of a press box remodel project. The existing 100 kW generator was too small to be reused but had to remain in place to provide power to other existing loads. This presented some unique challenges in determining which existing loads would remain in place and how to reroute feeders to allow these loads to remain. Ultimately, we were able to define a good break point in the existing system, which enabled us to remove loads as necessary and minimize cable rerouting and reconnection.
CSE: What is your primary choice for backup, standby, or emergency power?
McKinlay: For sports venues the common source standby or emergency power would be an oil-fired generator. In addition we would recommend two sources from the electrical utility and UPS power with batteries to serve broadcast systems. Use of the grid supply as backup and generator power for the game can ensure minimum switch-over time with UPS systems to achieve FIFA broadcast compliance, for example.
Evans: Because the loads are too large for batteries, generators must be used to provide the secondary power for these facilities. Some of the specific loads (e.g., emergency lighting) can be provided via battery backup.
Lewis: The choice for providing backup power has much to do with the size of the project and the project budget. For large projects, our first choice is to provide a diesel generator sized in accordance with NFPA 110 to power both emergency and legally required standby loads. However, smaller projects often cannot afford this. In these instances, we typically will use emergency batteries to provide backup power to emergency light fixtures.
CSE: What low- and medium-voltage challenges have you encountered in these facilities, such as communications, satellite uplinks, etc.?
Lewis: Low-voltage cabling pathways tend to be a challenge. Many end users like to use cable tray as the primary pathway because of accessibility and ease of maintenance. However, it can be difficult to provide adequate access to cable tray because of coordination with ductwork, piping, light fixtures, conduit, etc. Also, because cable tray must be accessible, it cannot be located above hard ceilings. It can be routed above lay-in ceilings, but this reduces some of the flexibility of cable tray. Additionally, limited structure heights often create significant challenges in locating the tray.