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Part 2: Keys To Backup Power System Success: Features, Flexibility, And Redundancy
By Michael Fluegeman
March 2014 -
Power & Communication Article Use Policy
Backup power system success begins with features, flexibility, and redundancy to fit the need. Name brand, quality equipment with adequate local sales and service support should be sourced.
Once installed, backup power systems should be thoroughly commissioned. This includes operation of all components and key features in all applicable modes (normal, bypass, failover, etc.), preferably under loads ranging from very light to full design load. Integrated system testing with actual loads connected and loaded (HVAC, UPS, etc.) including remote monitoring and BMS tie-in should be performed, culminating in multiple utility-power-fail "pull-the-plug" tests. Site-specific standard and emergency operating procedures should be developed in advance of commissioning. The commissioning phase of the project is the best opportunity to validate procedures and train operators.
Ideally, operators become comfortable actually performing manual operation of generators and ATS. However, the equipment is highly automated. The goal for operator training on backup and support equipment is for operators to be able to observe normal automatic operation, to know when not to intervene (when to keep one's hands in one's pockets), and to recognize when something does not look or sound right.
A classic example of an operator fumble with a backup generator system supporting a UPS system plays out like this: The generator is running, the open-transition ATS is in "emergency" position, with the generator supporting the UPS, and the UPS is then transferred to bypass (no battery backup available). The previous steps are often manually performed during various maintenance tasks, although the system can find itself in this state automatically or through a combination of auto and manual actions. At this point it is mandatory to put the ATS into manual or test mode or to open the "normal" source to prevent an ATS re-transfer. If the ATS is allowed to remain in auto mode, and if normal utility then becomes available (or was never off) the ATS will time out, then automatically transfer back to the utility. The problem occurs if the UPS is still in bypass and is not ready for the transfer. The UPS cannot provide battery backup for the short-term ATS re-transfer power bump when it is in bypass. Then the critical equipment supported by the UPS sees a power failure and crashes.
Regular inspections are needed to ensure readiness. Unless the following items are remotely monitored with alerts programmed, direct observation is required on at least a weekly basis, sometimes as often as daily:
Regardless of how often the above items are checked, any time maintenance of any sort is performed on any of this equipment, or on any equipment in the same general area, always re-check these items after all work is complete and service personnel have left the area.
Part 1: Standby Generators Require Regular Testing, Maintenance, Exercising, And Inspection
Part 3: Exercise Standby Generators To Keep Them In Fighting Shape
Part 4: Preventive Maintenance Is Critical To Dependable Standby Generators