Tan delta
Updated 2026-10-27
Data records
- Tan delta is the tangent of the loss angle of an insulation system, the angle by which the current through the insulation under alternating voltage departs from a purely capacitive current. It is the dissipation factor expressed as a ratio, and it rises as the insulation takes up moisture, ages or develops conductive paths.
- The term is written Tan delta. Value: Tan delta.
- In cable diagnostics a tan delta measurement is made at the test voltage with the measuring head at high voltage potential close to the cable under test, and the voltage, the current and the loss factor are displayed graphically while the test runs. The display lets a deteriorating cable be recognized early and the voltage load on it kept to a minimum, and the loss factor is used to recognize and quantify aging effects such as moisture and water treeing.
Elsewhere in the family
- Cable Tan Delta related entry on Electrical Testing Reference
- Insulation Power Factor Dissipation Factor related entry on Circuit Breaker Reference
- Insulation Power Factor Dissipation Factor related entry on Electrical Testing Reference
- Insulation Power Factor Dissipation Factor related entry on Motor Testing Reference
- Insulation Power Factor Dissipation Factor related entry on Revenue Metering Reference
- Insulation Power Factor Dissipation Factor related entry on Switchgear Testing Reference
- Insulation Power Factor Dissipation Factor 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.
- Megger product page, Tan Delta Test Attachment, web page edition, Megger. Held as: Public page. Publisher page
Changelog (7 entries)
| Date | Revision | Change |
|---|---|---|
| 2026-10-27 | created (gloss.tan-delta.definition) | |
| 2026-10-27 | review_status unreviewed -> software_reviewed (gloss.tan-delta.definition) | |
| 2026-10-27 | created (gloss.tan-delta.title) | |
| 2026-10-27 | review_status unreviewed -> software_reviewed (gloss.tan-delta.title) | |
| 2026-10-27 | created (gloss.tan-delta.usage) | |
| 2026-10-27 | revised (gloss.tan-delta.usage) | |
| 2026-10-27 | review_status unreviewed -> software_reviewed (gloss.tan-delta.usage) |
Cite this page
Cite the governing standard for the fact itself; cite this page as the finding aid.
"Tan delta." Test Instrument Reference. 2026-10-27. https://www.testinstrumentreference.com/glossary/tan-delta/.
Test Instrument Reference, Tan delta (Oct. 27, 2026), https://www.testinstrumentreference.com/glossary/tan-delta/.
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title = {Tan delta},
howpublished = {\url{https://www.testinstrumentreference.com/glossary/tan-delta/}},
organization = {Test Instrument Reference},
publisher = {Test Instrument Reference},
year = {2026},
note = {last substantive change 2026-10-27}
}{{cite web |title=Tan delta |website=Test Instrument Reference |publisher=Test Instrument Reference |url=https://www.testinstrumentreference.com/glossary/tan-delta/ |date=2026-10-27 |access-date=}}