Electrical Testing Reference

Dissipation factor

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The dissipation factor of an insulation system is the tangent of its loss angle, a dimensionless measure of the dielectric loss that the insulation shows under an alternating voltage. [1] [2] It is closely related to the insulation power factor, and ANSI/NETA ATS-2025 and ANSI/NETA MTS-2023 refer to the two quantities together. [3] [4] [5]

Definition

Dielectric losses are the energy dissipated as heat when an alternating electric field acts on an insulating material, and their principal measure is the loss tangent, tan δ. The dissipation factor is numerically equal to tan δ and expresses the ratio of resistive to reactive power in the material. [6] [1]

Seen in terms of current, an alternating voltage applied to insulation drives a component in phase with the voltage, which corresponds to the losses, and a component in quadrature, which corresponds to the capacitance of the insulation; the dissipation factor is the ratio of the first to the second. [2]

Units

As a ratio of two currents the dissipation factor is a dimensionless quantity, and the NIST Guide to the SI notes that the symbol for the unit one is generally omitted when such values are stated. [7] [2]

Relationships

The power factor of the same insulation equals the cosine of the angle by which the current leads or lags the applied voltage, which equals the sine of the loss angle. [3] The dissipation factor is the tangent of that loss angle, so the two quantities describe the same angle through different trigonometric functions. [2]

Used in

The quantity is measured in the insulation power factor and dissipation factor test. [8] [9] ANSI/NETA ATS-2025 Table 100.3 gives recommended values for liquid-filled transformers, regulators and reactors at a reference temperature, and ANSI/NETA MTS-2023 Table 100.3 gives maintenance test values for the same classes. [4] [5] For liquid-filled transformers the acceptance standard calls for the measurement at clause 7.2.2.B.4. [10]

Notes

  1. IEEE Technology Navigator, web page edition. IEEE Technology Navigator describes the loss tangent, tan δ, as the principal measure of dielectric loss, where δ is the loss angle of the dielectric, and states that the dissipation factor is numerically equal to tan δ and expresses the ratio of resistive to reactive power in the material. Datum qty.dissipation-factor.technav-loss-tangent
  2. Electrical Testing Reference editorial taxonomy, 2026-10 edition. The dissipation factor of an insulation system under an alternating voltage is the tangent of its loss angle, which equals the ratio of the in-phase, resistive component of the current through the insulation to its quadrature, capacitive component. Datum qty.dissipation-factor.definition
  3. Electrical Testing Reference editorial taxonomy, 2026-10 edition. The power factor of an insulation system is the cosine of the phase angle between the applied alternating voltage and the resulting current, which equals the sine of the loss angle. Datum qty.dissipation-factor.power-factor
  4. ANSI/NETA ATS-2025, clause Table 100.3. ANSI/NETA ATS-2025 Table 100.3 gives recommended dissipation factor or power factor values at a reference temperature for liquid-filled transformers, regulators and reactors. Datum qty.dissipation-factor.ats-table
  5. ANSI/NETA MTS-2023, clause Table 100.3. ANSI/NETA MTS-2023 Table 100.3 gives dissipation factor or power factor maintenance test values at a reference temperature for liquid-filled transformers, regulators and reactors. Datum qty.dissipation-factor.mts-table
  6. IEEE Technology Navigator, web page edition. IEEE Technology Navigator defines dielectric losses as the energy dissipated as heat when an alternating electric field is applied to an insulating material. Datum qty.dissipation-factor.technav-dielectric-loss
  7. NIST SP 811, web page updated 2025-08-18 edition, clause Table 3, note b. The NIST Guide to the SI notes that the symbol for the derived unit one is generally omitted when values of dimensionless quantities are stated. Datum qty.dissipation-factor.unit-one
  8. ANSI/NETA ATS-2025, clause 7.24.1.B.7. Insulation Power Factor Dissipation Factor is addressed in ANSI/NETA ATS-2025. Datum tests.insulation-power-factor-dissipation-factor.governed-by.ansi-neta-ats(provenance pending)
  9. ANSI/NETA MTS-2023, clause 7.24.1.B.7. Insulation Power Factor Dissipation Factor is addressed in ANSI/NETA MTS-2023. Datum tests.insulation-power-factor-dissipation-factor.governed-by.ansi-neta-mts(provenance pending)
  10. ANSI/NETA ATS-2025, clause 7.2.2.B.4. Insulation Power Factor Dissipation Factor is specified for liquid-filled transformers in acceptance testing at clause 7.2.2.B.4 of ANSI/NETA ATS-2025.Value: liquid-filled transformers. Datum tests.insulation-power-factor-dissipation-factor.equipment.transformer-fluid.acceptance(provenance pending)

Data records

  • ANSI/NETA ATS-2025 Table 100.3 gives recommended dissipation factor or power factor values at a reference temperature for liquid-filled transformers, regulators and reactors. Source: ANSI/NETA ATS-2025, clause Table 100.3. Verified 2026-10-13. Review status: Agent reviewed. Record qty.dissipation-factor.ats-table
  • The dissipation factor of an insulation system under an alternating voltage is the tangent of its loss angle, which equals the ratio of the in-phase, resistive component of the current through the insulation to its quadrature, capacitive component. Source: Electrical Testing Reference editorial taxonomy, 2026-10 edition. Verified 2026-10-13. Review status: Agent reviewed. Record qty.dissipation-factor.definition
  • ANSI/NETA MTS-2023 Table 100.3 gives dissipation factor or power factor maintenance test values at a reference temperature for liquid-filled transformers, regulators and reactors. Source: ANSI/NETA MTS-2023, clause Table 100.3. Verified 2026-10-13. Review status: Agent reviewed. Record qty.dissipation-factor.mts-table
  • The power factor of an insulation system is the cosine of the phase angle between the applied alternating voltage and the resulting current, which equals the sine of the loss angle. Source: Electrical Testing Reference editorial taxonomy, 2026-10 edition. Verified 2026-10-13. Review status: Agent reviewed. Record qty.dissipation-factor.power-factor
  • IEEE Technology Navigator defines dielectric losses as the energy dissipated as heat when an alternating electric field is applied to an insulating material. Source: IEEE Technology Navigator, web page edition. Verified 2026-10-13. Review status: Agent reviewed. Record qty.dissipation-factor.technav-dielectric-loss
  • IEEE Technology Navigator describes the loss tangent, tan δ, as the principal measure of dielectric loss, where δ is the loss angle of the dielectric, and states that the dissipation factor is numerically equal to tan δ and expresses the ratio of resistive to reactive power in the material. Source: IEEE Technology Navigator, web page edition. Verified 2026-10-13. Review status: Agent reviewed. Record qty.dissipation-factor.technav-loss-tangent
  • The NIST Guide to the SI notes that the symbol for the derived unit one is generally omitted when values of dimensionless quantities are stated. Source: NIST SP 811, web page updated 2025-08-18 edition, clause Table 3, note b. Verified 2026-10-13. Review status: Agent reviewed. Record qty.dissipation-factor.unit-one

Related entries

Sources

  • ANSI/NETA ATS-2025, Acceptance Testing Specifications for Electrical Power Equipment and Systems, 2025 edition, NETA. Cited: clause Table 100.3; clause 7.24.1.B.7; clause 7.2.2.B.4. Held as: Purchased single-user copy. Publisher page
  • ANSI/NETA MTS-2023, Maintenance Testing Specifications for Electrical Power Equipment and Systems, 2023 edition, NETA. Cited: clause Table 100.3; clause 7.24.1.B.7. Held as: Purchased single-user copy. Publisher page
  • Electrical Testing Reference editorial taxonomy, Electrical Testing Reference editorial taxonomy of test methods, 2026-10 edition, Electrical Testing Reference. Held as: Own observation.
  • IEEE Technology Navigator, Dielectric losses (IEEE Technology Navigator topic page), web page edition, IEEE. Held as: Public page. Publisher page
  • NIST SP 811, NIST Guide to the SI, Chapter 4: The Two Classes of SI Units and the SI Prefixes, web page updated 2025-08-18 edition, NIST. Cited: clause Table 3, note b. Held as: Government work. Publisher page

Obtaining the documents

Changelog (20 entries)
DateRevisionChangeReasonBy
2026-10-131created hand-written exemplar for the article generator (Task 10)agent
2026-10-13created (qty.dissipation-factor.ats-table)method fact restated from the licensed-copy digest (Task 10 exemplars)agent
2026-10-13provenance noted (qty.dissipation-factor.ats-table)locator from the NETA index table of contents (section and table numbers, titles and tables_referenced only); no body text usedagent
2026-10-13reviewed (qty.dissipation-factor.ats-table)fresh-context review task-10-exemplars-review.md + fix round 1agent
2026-10-13created (qty.dissipation-factor.definition)editorial definition of general physics (Task 10 exemplars)agent
2026-10-13reviewed (qty.dissipation-factor.definition)fresh-context review task-10-exemplars-review.md + fix round 1agent
2026-10-13created (qty.dissipation-factor.mts-table)method fact restated from the licensed-copy digest (Task 10 exemplars)agent
2026-10-13provenance noted (qty.dissipation-factor.mts-table)locator from the NETA index table of contents (section and table numbers, titles and tables_referenced only); no body text usedagent
2026-10-13reviewed (qty.dissipation-factor.mts-table)fresh-context review task-10-exemplars-review.md + fix round 1agent
2026-10-13created (qty.dissipation-factor.power-factor)editorial definition of general physics (Task 10 exemplars)agent
2026-10-13reviewed (qty.dissipation-factor.power-factor)fresh-context review task-10-exemplars-review.md + fix round 1agent
2026-10-13created (qty.dissipation-factor.technav-dielectric-loss)read from the public IEEE Technology Navigator topic page (review fix 6)agent
2026-10-13reviewed (qty.dissipation-factor.technav-dielectric-loss)fresh-context review task-10-exemplars-review.md + fix round 1agent
2026-10-13created (qty.dissipation-factor.technav-loss-tangent)read from the public IEEE Technology Navigator topic page (review fix 6)agent
2026-10-13reviewed (qty.dissipation-factor.technav-loss-tangent)fresh-context review task-10-exemplars-review.md + fix round 1agent
2026-10-13created (qty.dissipation-factor.unit-one)read from the government page (Task 10 exemplars)agent
2026-10-13reviewed (qty.dissipation-factor.unit-one)fresh-context review task-10-exemplars-review.md + fix round 1agent
2026-10-13created (tests.insulation-power-factor-dissipation-factor.equipment.transformer-fluid.acceptance)seeded from the test taxonomyagent
2026-10-13created (tests.insulation-power-factor-dissipation-factor.governed-by.ansi-neta-ats)seeded from the test taxonomyagent
2026-10-13created (tests.insulation-power-factor-dissipation-factor.governed-by.ansi-neta-mts)seeded from the test taxonomyagent

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BibTeX

@misc{etr-quantities-dissipation-factor-rev1,
  title = {Dissipation factor},
  howpublished = {\url{https://www.electricaltestingreference.com/quantities/dissipation-factor/rev/1/}},
  organization = {Electrical Testing Reference},
  publisher = {Electrical Testing Reference},
  year = {2026},
  note = {Revision 1; last substantive change 2026-10-13}
}

Wikipedia

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