By Bhavesh Patel, Director of Marketing, ASCO Power Technologies
The recently adopted Article 708 of the National Electrical Code (NEC) is aimed at protecting the economy from critical power infrastructure failure. It also could transform distributed generation. Article 708 defines a new type of alternate power systemCritical Operations Power System (COPS)that will enhance power reliability in times of natural and man-made disasters for five economy-critical sectors.
The affected sectors (outside of the electric power sector) are information/communications, banking/finance, oil/gas, rail/air transport and water; of which requires electricity to maintain critical operations. Driven by the Department of Homeland Security, Article 708 reflects the work of public and private organizations along with agencies that develop standards such as the National Fire Protection Association. The objective goes beyond other measures to enhance power reliability for sectors critical to the nation’s well-being. Hurricane Katrina and other weather-related causes of power outages along an aging power grid helped pushed creation of Article 708.
Article 708 addresses installation, operation, monitoring, control and maintenance of systems intended to supply, distribute and control electricity to vital operations in the event of disruption. Codes at the federal, state and municipal levels, “authorities having jurisdiction” (AHJs) or facility engineering documentation can establish the need for COPS in any of the six sectors.
As states adopt Article 708, it will affect the design, commissioning and maintenance processes for alternate systems. It is hard to predict when states or municipalities will adopt the 2008 Code. However, states such as Florida, Idaho, Iowa, Kentucky, Louisiana, Minnesota, Nebraska, North Carolina, North Dakota, Ohio, Oregon, Texas, Utah, Washington, Wisconsin and Wyoming adopted the 2005 Code. It’s a good bet they, too, will adopt the 2008 Code.
Critical power systems may wind up operating in tandem with utility power grids, making true distributed generation a common practice. Article 708 allows COPS to be a peak shaving source, provided that load management capabilities enable loads to be added and shed as required during an emergency.
Changes to other sections of the Code enhance the opportunity to use COPS to complement utility power. Section 700.9 will enable a distribution switchboard to separate feeders for different COPS by using different vertical sections of the switchboard. Section 702.5 will better define load management strategies using manual and automatic power transfer switch capabilities for these alternate power systems. The process for adding and shedding loads by COPS will be more flexible.
Emission limits may tighten, too. States limit the number of hours that engine-generators can operate as a way to control emissions. Those limits will probably tighten, especially in California and a few other states. Besides limiting operating hours, a push to clean up engine exhaust also could occur. It will be important to consider environmental limitations governing wider use of COPS as distributed generation.
In general, Article 708 addresses wiring, surge suppression, grounding, risk assessment, power transfer switches and other systems. Using power transfer switches as an example illustrates the differences between Articles 702 and 708.
Power transfer switches that comply with Article 702 and 708 must be suitable for their intended use and prevent the inadvertent interconnection of primary and alternate power systems. This means transfer switches must be evaluated to Underwriters Laboratories Standard for Safety, Transfer Switch Equipment (UL 1008). The similarities, however, end there. Power transfer switches installed in a critical operations power system must be automatic and suitable for an emergency power system. The transfer switch must be electrically operated and mechanically held and may supply critical operations power systems only.
Critical operations power systems also must be isolated from non-critical power systems. This means transfer switches installed in a critical operations power system have more in common with the requirements for transfer switches installed in emergency (Article 700) or legally required power systems (Article 701). Article 708 also differs from Articles 700 and 701 in terms of the time to transfer between the primary power source and the emergency or alternate power source. For emergency power systems, mandated transfer time is 10 seconds or less. For legally required standby power systems, it’s 60 seconds or less.
No transfer time requirement exists for a critical operations power system. That’s because it’s assumed that time to transfer between the primary and alternate sources must occur before the stored energy in batteries or flywheels falls below acceptable levels.
Besides power transfer switch operational requirements, Article 708 also calls for:
- Automatic engine-generator start up
- A minimum of 72 hours worth of fuel on site
- Ability to connect a portable engine-generator to COPS when the COPS has only a single engine-generator
- Secure, redundant and fire-protected power and fuel sources that are above the 100-year flood plain
- Two hours of fire resistance protection for power transfer switches, transformers, panel boards and other equipment
- Witness tests performed under full load
- More oversight and paperwork than in previous Code versions.
For power utilities, Article 708 could prove a catalyst to wider application of distributed generation for utilities and their customers. That presents the challenges of safe interconnection for personnel and equipment, two-way power flow and the accompanying metering and billing issues. It’s just the thing to usher in a new year and perhaps a new era in helping satisfy power consumption.