The design of the Atlanta airport incorporated the best practices of airport design, but this did not provide the necessary system resiliency required to avoid a massive power outage. It is also interesting to note that the design documents were reviewed by the contractor, the power company and FAA based on airport design concepts so the deficiencies that contributed to the outage were not recognized nor properly addressed. This airport along with many other public facilities now need to implement mission critical design concepts.
While the mission critical design community has been primarily involved in financial, credit card, health care and broadcast industries, the Atlanta airport experience shows the need to implement these design concepts in many more areas where critical facilities and ultimately public safety are at risk.
Facilities Engineering Associates (FEA) was founded in the late 1980’s with the specific goal of providing professional engineering services for designing mission critical facilities. We were fortunate to be involved in the formation and growth of the industry, which became an established design concept in the 1990’s. During that time the 7x24 Exchange, the leading knowledge exchange for those who design, build, operate and maintain mission critical infrastructures, was founded to promote dialog between these groups.
As the design concepts evolved, the following criteria were developed:
Reliability – the concept where the design is analyzed for its inherent reliability to ensure that the necessary 9’s reliability is provided for the specific system requirement.
Redundancy – the concept where multiple units are deployed with excess capacity to serve the load even if there are equipment failures – these included N+1, N+2 and N+N redundancy. Redundancy has evolved to the point where super critical infrastructures now deploy multiple facilities that can duplicate all functions that were handled by a failed facility.
Fault Tolerance – the design needs to ensure that equipment or system faults are isolated without inverse impact on the facility so that the remaining systems can continue to serve the load.
7x24xForever – the design concept where any necessary maintenance or system upgrade can be implemented without shutting down nor loss of any of the functionality of the facility.
Meeting these design criteria requires special attention as to how each system is configured and how it will interact with all other critical systems, not only in ‘normal’ operation, but also during an emergency or equipment failure. In addition to meeting the stated design criteria the design professional needs to be well versed in non-design issues as outlined below.
FEA approaches a client with the intent of not only providing professional design services, but also informing them of the nuances of “mission critical design” philosophes. While these basic principles are not difficult to define, they require specialized understanding to implement.
Atlanta Airport Design Shortages:
The power failure at the Hartsfield-Jackson Atlanta International Airport is an excellent example of a facility that needs to implement mission critical design concepts. While it is difficult to get a definitive explanation of what exactly occurred, we do know these basic facts:
There was a massive power outage to the entire airport affecting multiple redundant substations and feeders.
There was an emergency power failure at one terminal.
While I am certain the design incorporated all characteristics of high reliable, efficient airport design, it does not seem, based on the information, that mission critical design concepts were implemented.
Multiple redundant feeders were deployed as a redundant power source which either originated or were routed through common substations and underground tunnels so a fire in the substation or tunnel system negated the reliability, fault tolerance and redundancy of the design.
Our projects have encountered this exact concern regarding utility power redundancy and reliability; so we therefore design redundant on-site power systems that are totally divorced from the utility power source including routing and points of interconnection.
The entire facility is served with redundant systems which are totally physically separated until they meet at the load.
Emergency power feeds to the terminals were routed through the common feeder underground system that was affected by the substation fire that again negated the reliability, fault tolerance and redundancy of the design.
Our projects have designed emergency power systems totally independent of the power company and fully capable of serving the entire load. These systems are N+N redundant whereas both systems are fully configured to serve the entire load. Each system is totally independent and physically isolated from the other including all sources and feeders which are routed through independent diverse paths to the load.
Do to the length of the outage the emergency generator systems should have been routinely tested with load and stress tested to insure they were capable of long term operation. Our clients normally test their systems periodically and we have a client that has operated on “generator” power for in excess of 7 days twice in the past 5 years.
These outages show the need to implement mission critical design concepts but also non-design issues – i.e. All redundant feeders need to be served by different sources, diverse routing of redundant feeders, total isolation of emergency power systems from the normal power system, diverse routing of “normal” and “emergency” feeders.
Standard airport design does not include these nuances that are necessary to insure resilient and reliable systems. While the airport design was appropriate at the time, it now falls short of the present critical functionality of the facility.
A new benchmark needs to be advanced for not only airports, but other public facilities to include mission critical design concepts to meet these added requirements.