Your questions answered: The electrical system’s role in designing for resiliency
During the webcast, several questions were left unanswered. Additional info was provided by the presenters
During the Dec. 2, 2020, webcast titled, “The electrical system’s role in designing for resiliency,” the presenters received several additional questions. Read the responses here from:
- Jeremy Gustafson, Business Development Manager, Siemens Industry Inc.
- Zach Goldsworthy, National Healthcare Market Leader, Siemens Industry Inc.
Question: When is the safe power center required per NFPA 70: National Electrical Code in operating rooms with invasive procedures?
Siemens: NEC 517.19 (C) specifies the requirement of the receptacles within operating rooms.
Question: Does reliability consider nature-related issues: ice storms, tornadoes, hurricanes, earthquakes, etc.?
Siemens: Reliability needs to consider the natural weather conditions and the impacts they may have on the facility.
Question: Can you address the issue of utility line recloser operation?
Siemens: This is a great conversation to have with the local utility company to better understand how they operate and serve their clients. Recloser operation is done through relays and medium- and high-voltage applications. Hospital applications do not typically have distribution that would benefit from a recloser operation.
Question: What do you mean by radial feeder here?
Siemens: A radial service entrance has one electrical utility feeder that offers multiple single points of failure.
Question: For a green build project, when designing a switchgear room, what are the things that drive a top-down design versus the typical bottom-up design?
Siemens: For the main switchgear room, it is important to consider access to the outside (especially if the switchgear is the service entrance) and clearances where in the bottom up the team can specify the components and functionality.
Question: What about IR inspection windows? And arc flash suppression devices?
Siemens: IR windows and arc flash suppression devices are great examples of products that contribute to safe inspection and operation of the equipment, which positively impacts the resiliency of the facility.
Question: There are multiple sources or feeders, however, at any instant of time, is the hospital served by only one (radial) or multiple (loop) sources/ feeders together?
Siemens: Depends on the utility, some utility company provide multiple sources serving network transformers to a common bus at the service entrance. Other utility companies only allow a radial feed. This is a great discussion to have with the utility company ea
rly on as many utility companies offer special options for hospital service entrances.
Question: Please elaborate on metal enclosed switchgear that can limit impact if fault occurs in other section of switchgear.
Siemens: Metal enclosed and arc-resistant switchgear are great examples of products that contribute to safe operation of the equipment, which positively impacts the resiliency of the facility.
Question: Doesn’t the closed transition switchgear require significantly higher fault interrupting capability, which can drive up the cost for many devices?
Siemens: Yes, closed transition does increase the AIC rating required for the equipment.
Question: Does closed transition transfer switch only offer convenience for testing versus reliability?
Siemens: Yes, closed transition offers the convenience during testing that the end users and patients will not see an interruption.
Question: Is there any standard index like SAIDI SAIFI values for hospital?
Siemens: Unfortunately, no standard index exists for hospitals.
Question: Can you please repeat the website for recorded information of historical lightning strikes? is there information for lightning protection design?
Siemens: There are several resources:
- Remember to review the Lightning Frequency Isoceraunic Level for your project.
Question: Closed transition on redundant automatic transfer switches? Interlocked for synchronization?
Siemens: If the redundancy of the AT’s is done through a double ended lineup, utilizing a closed transition will add to the resiliency.
Question: What about connection of the power system to the building management system for notifying the owner of trouble or fault or power on generator? What about the power system being connected to the building management DCS or SCADA system to notify the owner in the event of problems, faults or generator running?
Siemens: Integration of the power system to the building automation system adds to the resiliency, and today is also becoming standard practice. I would consider analysis of the electrical meter loads and demand analysis to better understand how the electrical system is being utilized and responding.
Question: Is there a way to incorporate battery energy storage systems to increase resiliency in a hospital design?
Siemens: Yes. I would consider fuel cells or natural gas generators as the payback would be expected to be quicker. If batteries are added, it would be added off the load side of the transfer switch. To provide an added benefit to the owner review flywheel versus battery uninterruptible power supplies.
Question: Besides performing a short circuit analysis, isn’t a coordination study an aspect of electrical systems resiliency?
Siemens: No, the short circuit analysis is required to determine the proper AIC rating and the coordination study is part of selection of the circuit breakers to ensure a circuit breaker tripping minimizes the impact to the coordination.
Question: Wouldn’t the closed transition capability also require synchronizing equipment and may require additional protective relay equipment and more setting flexibility?
Siemens: Depending on the application and where the transition is occurring, yes. The closed transition would also require a higher AIC rating of the electrical equipment
Question: Are there parts of the USA where Siemens does not have a commercial or industrial power distribution presents due to the other manufacturers?
Siemens: Siemens has national coverage across the USA and North America. While there are always other distribution manufacturers in many of these markets, Siemens continues to focus on end users and have full coverage to support clients and end users.
Question: How about integration of large UPS systems?
Siemens: Depending on what the UPS serves and how it impacts the operations, this could also add resiliency to a facility. It’s important to consider what maintenance would be required for a UPS.
Question: Is something like lead acid batteries ever used to improve resiliency by providing essential power for direct current operated equipment or controls?
Siemens: Many hospitals use small battery UPSs to serve imaging, lab or pharmacy equipment. While these minimize interruptions during power outages and generator tests, they also become a maintenance nightmare for replacement costs (typically 3 to 5 years).
Question: For resiliency, we need to have two different power supply from the utility, correct?
Siemens: No, providing two different “power supplies from the utility” is one option. Unfortunately, sometime it’s not possible so resiliency will need to be added other ways.
Question: Could you please clarify if EPMS is recognized by NFPA 99 as essential system? If yes, is it directly called for and exactly in which category?
Siemens: Electrical power monitoring system is to process, analyze, store and share energy usage and status of the electrical system. It contributes to the resiliency but not part of the essential system, serving load.