Don’t Settle for “Better than Nothing”: Exercise Standby Systems with Load ENGINEERING SUB-COMMITTEE
duce engine performance and will re- quire periodic 100% load banking to clear, which is a costly service. How- ever, this load banking can be avoided if engines remain sufficiently loaded when they are exercised. With the high stakes invested in a standby power system, why is “no- load” testing so prevalent? There are many reasons that facility staff cite when asked this. • Politics: It is sometimes unpopular among personnel to have to deal with the effects of transferring load, as exemplified by flickering lights, and working around generators which are louder at full load. • Equipment Disruption: Large motor loads can be disrupted when they are suddenly off without notice. This can cause alarms which have to be manually acknowledged before the equipment is placed back into service. • “It might not work”: Staff are sometimes worried that transfer testing could encounter a failure and inadvertently cause a temporary local outage, requiring an immediate response on an otherwise uneventful day. However, it is much better when capable personnel is in attendance. Otherwise, such a failure would not rear its ugly head until an actual utility outage. The response will likely be much more panicked in this scenario, with personnel not being poised to manually restore power. to encounter such a failure on a typical day so that it can be proactively addressed
A lthough the first quarter of the 21st century has come and gone, utility power outages remain unpre- dictable and continue to cause major disruptions across the nation. It is of utmost importance that any facility which depends on power continuity for the preservation of assets to en- sure that their transfer equipment, as well as their standby power sources, will execute the task that they were installed for; to operate dutifully in the event of a utility power loss. It is a common owner misconception that exercising generators without load is a sufficient test for a stand- by power system. The reality is that cranking engines and letting them run at idle only covers a small portion of the power restoration process. Prov- ing that the generators start when called will not identify the following failure modes: • Failure of two or more generators to parallel in an acceptable time • Failure of the generators to sustain or share facility load • Failure of the Auto-Transfer system to detect acceptability of generator power • Failure of the Auto-Transfer system to transfer loads to the standby power source • Failure of the Auto-Transfer system to re-transfer loads upon restoration of utility power Furthermore, it can be deleterious to engine health to exclusively run gen- erators at low or no load. For diesel generators, this will cause a build- up of un-combusted diesel sludge known as “wet-stacking” in the en- gine’s exhaust pathway. This can re-
Joe Kendall Chair, Engineering Sub-Committee Schneider Electric
18 | Summer 2026 POWERLINE
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