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A dependable substitute power:
The role of generators


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To protect critical loads in facilities such as data centers, hospitals, pumping stations, and processing plants during normal utility failure, it is crucial for engineers to make informed decisions regarding proper generator size and operation methods. Engine-driven generators are considered the optimal candidate for standby and emergency power. It is important to ensure that generators are appropriate for the specific application and can supply the required power to the loads under designed conditions. The following major technical codes and standards should be reviewed and considered when choosing a generator: International Building Code, NFPA 70, NFPA 110, NFPA 101, IEEE 142, IEEE 493, IEEE 519, IEEE 602, IEEE 666, and the EPA regulations for emissions control.


Site constraints such as environmental impact, local ordinances, fuel facilities, site infrastructure, and maintenance preferences should also be taken into account when evaluating potential locations for the generators. Prime mover selection, such as diesel engines, gas engines, or gas turbines, should also be considered. When selecting prime movers, it is important to evaluate off-site fuel reliance, load pickup and drop, and maintenance concerns.


Engine-driven generators should be sized correctly for various loading scenarios and to supply the required power to perform the designed function. During load steps, such as a motor starting across the line, high inrush currents may cause substantial voltage dips. To reduce the voltage and frequency dips, soft starters for motors or variable frequency drives that can regulate the output voltage and frequency can be used.


When determining whether generators with utility systems should be paralleled, capacity, redundancy, and compliance should be considered. A paralleled system allows additional generator sets to provide combined power during times of higher loads. It is important to carefully analyze the electrical system to determine how much fault current will be injected to assess the risk of generator fault contribution.

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