Once the design of the system is well documented and understood, it is important to identify critical loads that will require power in the event of a power outage. Typically, standby generation cannot be provided for all of the facility’s loads, so decisions need to be made as to what equipment is absolutely essential during the outage. Once identified, these loads should be clearly marked on the one-line diagrams as being "critical loads."
Depending on the importance of the critical loads and the possibility of being without power for a given period of time, you may consider installing an uninterruptible power supply (UPS) and a permanent standby generator (with auto-start) to power certain equipment. It is imperative that the running load of each critical circuit (measured in amperes) be known so that you know what size generator(s) will be required. The kilowatt and voltage ratings of each generator needed should be readily available prior to the outage to expedite your response.
If portable generation is the best alternative for your facility, but purchasing a standby unit is impractical, you may want to arrange a rental agreement with a dependable local vendor. Be sure to consider such things as how many generators they have in stock, how they will be delivered, what is the guaranteed response time, and what service is included if a generator has problems. Also, find out where you rank on their list of priority customers. When the outage happens, everyone will be looking for rental generators.
You need to plan how each generator will be connected during the outage. Is it practical to install manual transfer switches near the critical panels ahead of time so they are available to easily transfer the load to the generators? Are spare cables, properly sized for the load, stored with the generator(s) to ensure the hook-up can be done quickly? Has the rotation of three phase circuits (if any) been pre-determined and labeled to ensure proper connection of the generator to the critical loads? Do you have formal written procedures explaining how to connect each generator to its emergency loads? Is the plan in accordance with all national and local electrical codes? Is your staff adequately trained to do this work? If not, make arrangements with an experienced, reliable contractor to provide these services.
Once you know your critical circuits and their corresponding generator ratings, you should develop testing procedures to ensure that the generators can carry the critical loads. The installed standby generators should be tested quarterly under actual load conditions. If this is not practical, at the very least each generator should be started and run for approximately 45 minutes each month. Make sure that generator testing meets all requirements for state and federal emissions regulations. Also make sure that each generator fuel tank is full and that you know where and how to get fuel during the course of the outage. Test your fuel for the presence of water and replace fuel that is more than one year old.
If your facility has computer loads or communications systems that utilize a UPS to ride through short-term outages, you should develop procedures for having an orderly shutdown. Typically, a UPS will provide power for only a short period of time (15-60 minutes) to allow you to back-up system and data files, and bring the systems down. Preparing for this scenario now, and performing practice runs, will enable smooth and decisive response during an extended outage and help avoid lost data.