Very low frequency (VLF)
Updated 2026-10-27
Data records
- Very low frequency, in high-voltage testing, denotes an alternating test voltage at a frequency far below the power frequency. It is used so that a compact source can energize the large capacitance of a long cable or a large machine winding with alternating stress rather than with direct voltage.
- The term is written Very low frequency (VLF). Value: Very low frequency (VLF).
- Compared with a power frequency source, a very low frequency source for the same high voltage test is far smaller, lighter and cheaper, which matters most on highly capacitive loads such as shielded power cables and large machine windings. The capacitance of a cable plays only a small part in a steady direct voltage resistance measurement but a major part under alternating voltage, including very low frequency, which is the condition a cable sees in service.
Elsewhere in the family
- Cable Tan Delta related entry on Electrical Testing Reference
- Dielectric Withstand related entry on Circuit Breaker Reference
- Dielectric Withstand related entry on Electrical Testing Reference
- Dielectric Withstand related entry on Motor Testing Reference
- Dielectric Withstand related entry on Revenue Metering Reference
- Dielectric Withstand related entry on Switchgear Testing Reference
- Dielectric Withstand related entry on Transformer Testing Reference
Sources
- Electrical Testing Reference editorial taxonomy, Electrical Testing Reference editorial taxonomy of test methods, 2026-10 edition, Electrical Testing Reference. Held as: Own observation.
- HV Diagnostics FAQ page, FAQs, web page edition, HV Diagnostics. Held as: Public page. Publisher page
Changelog (7 entries)
| Date | Revision | Change |
|---|---|---|
| 2026-10-27 | created (gloss.very-low-frequency.definition) | |
| 2026-10-27 | review_status unreviewed -> software_reviewed (gloss.very-low-frequency.definition) | |
| 2026-10-27 | created (gloss.very-low-frequency.title) | |
| 2026-10-27 | review_status unreviewed -> software_reviewed (gloss.very-low-frequency.title) | |
| 2026-10-27 | created (gloss.very-low-frequency.usage) | |
| 2026-10-27 | revised (gloss.very-low-frequency.usage) | |
| 2026-10-27 | review_status unreviewed -> software_reviewed (gloss.very-low-frequency.usage) |
Cite this page
Cite the governing standard for the fact itself; cite this page as the finding aid.
"Very low frequency (VLF)." Test Instrument Reference. 2026-10-27. https://www.testinstrumentreference.com/glossary/very-low-frequency/.
Test Instrument Reference, Very low frequency (VLF) (Oct. 27, 2026), https://www.testinstrumentreference.com/glossary/very-low-frequency/.
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title = {Very low frequency (VLF)},
howpublished = {\url{https://www.testinstrumentreference.com/glossary/very-low-frequency/}},
organization = {Test Instrument Reference},
publisher = {Test Instrument Reference},
year = {2026},
note = {last substantive change 2026-10-27}
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