Developers and managers of hotels, resorts, casinos and timeshare communities in places where power quality is a prevalent issue—for example, the Caribbean, Central America and South America—understand the damage inconsistent voltage can cause all too well.
Non-essential systems shut down so compromised power can feed critical systems. Compressors shut oﬀ, and with them, so do refrigerators and freezers. Food safety becomes an issue, as do impending restaurant closures. Front desks are ﬂooded with calls and complaints. Refunds are issued. Guest-service scores drop.
In developed regions of the world, this is not a huge problem.
In much of the developing world, however, power quality problems remain a huge issue. Typically, a combination of diesel- powered electrical generation for primary systems with limited battery-powered UPSs for sensitive and critical loads are installed to provide backup power generation when voltage from the local grid falls out of spec. Due to the high cost of installation, maintenance and fuel, these backup systems are rarely designed to provide full power. Facility engineers must weigh the costs of backup systems – both initial and lifetime – against potential losses that might be incurred when non-essential systems go oﬄine.
But the formulas that dictate what constitutes acceptable risk, and therefore adequate backup, are changing as global competition heats up and as consumer expectations of an “invisible” quality power experience rise.
Until recently, decisions regarding backup power systems were binary. If the local grid could not be trusted to consistently supply “clean power,” engineers were forced to design systems that could temporarily sever a facility from the local source and provide independent backup. But a new technology, electronic voltage regulators (EVRs), transformers equipped with electronic on-load tap changers, now allow for a less binary formula that is also more economical and eﬃcient.
The American “sag” and the British “dip” refer to a voltage decrease to between 10% and 90% of nominal voltage for a duration of anywhere from one-half cycle (.008 seconds) to one minute.
Surges, or transients, are very short duration (sub-cycle) events of varying amplitude. Surges can be caused by equipment operation/failure or by weather events like thunderstorms. Even low- voltage surges can cause damage to electrical components if they occur frequently.
A brownout (undervoltage) is a decrease in voltage below 90% of its nominal value for more than one minute. Brownouts are generally a chronic problem in the developing world.