As a result of 9-11, Hurricane Katrina and other disasters, the Department of Homeland Security determined new requirements were needed to protect electrical systems at vital infrastructure facilities that could impact national security, the economy, and public health and safety. Article 708, Critical Operations Power Systems (COPS), was added to the NEC based on the need for standards that could strengthen homeland security. Since the requirements of Article 708 are quite detailed, we are dividing this article into two segments. Part 2 will appear in the November issue of PowerConnect.
Historically, the NEC has been focused on the installation of electrical equipment with an emphasis on fire safety. Article 708 significantly extends that scope to include operations, monitoring, control, and maintenance of the on-site power system for “Designated Critical Operation Areas” (DCOA). Article 708 was directed by the NEC’s Technical Correlating Committee Task Group on Emergency and Standby Power Systems for Homeland Security and created by Code-Making Panel 20.
With its traditional focus on fire safety, the NEC’s existing emergency system requirements (Article 700) are primarily concerned with evacuation. Article 708 is about maintaining operations through disastrous events, or defending in place, and it creates a new load category, COPS, legally required standby and optional standby. This allows municipal, state, and federal agencies as well facility engineering documentation to mandate COPS compliance as deemed appropriate. While police stations, emergency responders and-fianl key government operations will typically fall under this designation it could be extended to wastewater treatment operations, healthcare facilities and other businesses deemed to be critical to the public health and safety by the authority having jurisdiction (AHJ).
A significant element in developing COPS is risk assessments (NEC 708.4): In critical operations power systems, risk assessment shall be performed to identify hazards, the likelihood of their occurrence, and the vulnerability of the electrical system to those hazards. These hazards are to include natural and human-caused events. Once the risk evaluation has been performed, Article 708 requires an action plan to mitigate hazards that are not already mitigated by the minimum requirements of the code.
This is the point where the discussion becomes interesting. What are real risks and what is hype? What are the most common failure modes of back-up power systems? Though Article 708 was conceived in a post 9-11 environment filled with fear about terrorist attacks, how do intentional human-caused failures statistically compare with other potential failure modes for on-site back-up generators? Those more typical risks would include generator failure, bad diesel fuel, running out of fuel, human error, inadequate cooling, fire risks, wind, flooding, etc. Separating and prioritizing real, everyday sorts of risks from hype will be the practical challenge facing facility managers and systems designers in implementing a COPS.
Timothy Croushore, a P.E. from Allegheny Power and member of Code-Making Panel 20 said, “If the risks of a particular catastrophic event are realistic or probable at some level, then protection from that risk should be considered and implemented. However, if the risk of a particular event is very low, then protection from that risk needs to be considered appropriately.” (Source: NEC Digest, February 2007.)
An on-site back-up generator is a complex mechanical and electrical system. The reliability of this equipment is strongly affected by system design, installation, and preventive maintenance. Article 708 recognizes this by requiring a commissioning plan, baseline testing, and witness testing by the AHJ at start-up and periodically afterward. It also requires that the system have a documented preventive maintenance program, written records of testing, and means for testing all critical power systems “during” maximum anticipated load conditions (NEC 708.6(E)). The use of the word “during” seems to imply that the generators may need to be tested with the defined DCOA as the load versus a load bank. The testing practice of transferring critical operations onto a generator during peak usage is something that most facility managers typically avoid.
Though a single back-up generator can be well designed, properly installed, maintained and tested, as a complex system it still has hundreds of possible single point failures. Article 708 does not directly require parallel generation but does require single generator configurations to include a means for connecting a portable generator and requires that portable to “be available for use” whenever the generator is out of service for maintenance or repairs.
The AHJ will need to determine if “available for use” means connected to the power system. Given the focus on reliable power and the failure risk presented by a single generator configuration, the facility managers and system designers will have to convince the AHJ that this risk is adequately mitigated per the requirements of NEC 708.4(C). The case for using paralleled generation in the COPS design is further strengthened by current market innovations. Various manufacturers offer integrated generator paralleling solutions that are cost effective and feasible in smaller kW configurations—even as small as 100 kW.
If you have questions about the NEC Article 708 or any code issues, contact your authorized Generac Industrial Power distributor or dealer.