Reference
Glossary
Plain-language definitions of the terms used across our lessons and reports.
- Distribution Substation
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The point where transmission voltage steps down to distribution voltage and feeders branch out to carry power toward customers.
- Fault
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An unwanted connection, often to ground, that lets far more current flow than normal. Protective devices sense it and cut it off quickly.
- Feeder
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A distribution circuit that leaves a substation and carries power along streets to the transformers serving customers.
- Impedance (Percent)
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A transformer rating, given as a percent, that sets how much the voltage sags under load and how much current flows during a fault.
- kVA
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Kilovolt-amperes, the apparent power rating of a transformer. Divide it by the rated voltage to get the rated current a side can supply.
- Recloser
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A protective device that opens on a fault, then closes again a set number of times to test whether the fault has cleared before locking out.
- Transformer
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A device that uses a magnetic core and two windings to change voltage from one level to another, trading voltage for current.
- Turns Ratio
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The ratio of primary winding turns to secondary winding turns, which sets how much a transformer raises or lowers voltage.