Page 98 - Electrical Equipment Handbook _ Troubleshooting and Maintenance

TRANSFORMER COMPONENTS AND MAINTENANCE

TRANSFORMER COMPONENTS AND MAINTENANCE 4.27

erators). They feed the 4-kV and 600-V buses inside the plant when the normal power from
the UST and SST is lost. This type of power is considered more reliable than the power sup-
plied from the UST or SST. Most plants use large battery banks to supply emergency loads
(e.g., turbine emergency dc lube oil pump, generator stator emergency dc water cooling
pump, and generator emergency dc seal oil pump). Some plants use inverters to supply
emergency ac power from the battery bank to plant loads. The reliability of power supplies
in descending order is as follows:
1. Power from the battery banks (dc or ac through inverters) (most reliable)
2. Standby generators
3. Power through UST or SST (least reliable).

REFERENCE
1. Stanley D. Myers and J. J. Kelly, Transformer Maintenance Institute, Division of S. D. Meyers, Inc.,
Cuyahoga Falls, Ohio.

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