In the Know

The Case for Reactive Load Bank Testing for Stationary Engines | Part 1

For years, responsible facilities managers have been aware that they need backup electric power generation equipment at their businesses as “insurance” against threats such as lost time and equipment damage due to utility power interruptions. For critical and life safety institutions in the State of California, current Office of Statewide Health Planning and Development (OSHPD) regulations require backup power generation equipment be periodically tested in accordance with the manufacturer’s recommendations and that proper condition and maintenance be adequately recorded.

Backup generators, and the testing and maintenance associated with their operation, represent a substantial portion of any facility manager’s defense against these threats, but many managers (and some equipment and service providers) are not aware of their power generation equipment’s real-world weaknesses due to incomplete testing procedures of their equipment. Consequently, when utility power fails at their facility, the lights go out.

This paper explains the importance of addressing a facility’s emergency power generation system as a whole in order to identify system-wide weaknesses, and addresses and explains the difference between resistive and resistive/reactive load bank testing, and why the latter is necessary. This paper also addresses the importance of choosing a knowledgeable and experienced service provider as a partner in preparing a facility-specific emergency power generation maintenance and service plan.

Case Study | XYZ Hospital XYZ

Hospital in Southern California recently experienced a costly wake-up call in regard to their emergency power generation equipment. While XYZ’s maintenance engineers believed that their backup power system was state-of- the-art and ready to complete its mission, they did not consider the system as a whole, and the results were nearly catastrophic.

As of September 2012, XYZ had three 1000kW generators operating in parallel at their facility, with a fourth unit scheduled for delivery. While XYZ had tested each of their three original generators separately with a resistive load for the previous 11 years, their service provider recommended a full-system resistive/reactive test before the fourth generator’s arrival to check for problems with the existing units and isolate any possible problems encountered with the installation of the fourth generator. XYZ’s service provider connected a resistive/reactive load bank (see section three) at the main panel of XYZ’s generator system and, starting with their switchgear, began testing the units.

The results were surprising and potentially very dangerous. The resistive/reactive load bank test revealed that in an actual emergency, XYZ’s crucial systems would not function. At 50% generator capacity, XYZ’s service provider noticed problems with XYZ’s equipment: their switchgear was out of calibration, their alternators experienced heat problems and none of their voltage regulators worked properly. Their load-sharing and paralleling were asynchronous. If the hospital experienced a power outage, their system would fail completely. Almost identical circumstances happened at a California state prison with almost identical results.

Although the facilities managers at both locations followed the manufacturer’s instructions on their equipment to the letter, they both narrowly avoided catastrophic systems failure only by considering their emergency power generation equipment as a whole system and testing it as a whole.

Stationary Engines | Greater than the Sum of their Parts

Most business owners and facility managers rightly conclude that an emergency power generation system of some kind is important to insure that the resources and services essential to their business, such as water or compressed air, are not interrupted during a supply failure from their power utility. Other mission-critical operations such as hospitals depend on an uninterrupted supply of power because lives are at stake. Facilities managers at these businesses typically pride themselves on having chosen a knowledgeable and competent installer for their systems and carefully following their equipment manufacturer’s recommendations for testing and service intervals. However, despite their careful planning and thoroughly maintaining their equipment, many facilities managers are caught unaware when their equipment does not operate correctly—or at all—during an actual emergency. What goes wrong?

Any given emergency power generation unit is actually a complex system, or series of systems, working together to perform several duties at once. At the system’s heart is the “prime mover”, which burns fuel to create movement, which in turn is converted into electricity. Various discrete systems and sub-systems in the unit make this possible: alternators, regulators, switchgear, and various other additions to generation systems, all of which contribute to the system’s operation. These additional components can be products from different manufacturers, usually designed to interface with a number of makes, models, and sizes of diesel generators.

Like any other mechanical or electrical component, all are subject to failure and have varying maintenance needs: they all must be tested and serviced. But individually testing a series of components never answers the most important question of all: “How do you know that your system—and not merely its components—will work when it counts?”

In an emergency, a facility’s entire emergency power generation system will be stressed. Unlike in a series of short, component-by-component tests, the system must operate at full power, with all components working together. The stresses introduced by this kind of operation cannot be simulated by discrete tests of a system’s numerous individual components: automatic transfer switches, switchgear, load-sharing centers, voltage regulators, alternators, electrical cabling & connectors, ventilation, cooling systems, and fuel systems. Testing the system’s engine alone is insufficient.

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