Transformer Testing Reference

Data record equip.liquid-filled-transformers.usbr2005.thermal-aging

Verified 2026-10-29 Confidence: High

The Bureau of Reclamation's 2005 transformer manual states that high temperatures drastically shorten the life of the insulating materials in a transformer's windings and structures, and gives its rule of thumb in the datum value. Its section on core losses puts the life-halving step at the smaller temperature rise in the value; its section on infrared examination of radiators and cooling systems, on operation with reduced cooling, puts it at the range in the value. The figures are the manual's own, dated April 2005; the loading guide for the unit governs.

Value: life halves for each 8 °C of temperature rise (section 2.5); for an operating temperature increase of 8 to 10 °C (section 9.4.10)

ProvenanceReclamation Transformers 2005 supports data record equip.liquid-filled-transformers.usbr2005.thermal-aging, which is cited on the entry Liquid-filled transformers.SOURCEReclamation Transformers 2005Reclamation Transformers..Government work, clause 2.5 and 9.4.10DATA RECORDequip.liquid-filled-transformers.usbr2005.thermal-agingequip.liquid-filled-tran..Verified 2026-10-29ENTRYLiquid-filled transformersLiquid-filled transformers1 revision
Provenance. Where this record comes from and where it is used: the cited source, the record itself and the entry that cites it.
Provenance: the chain from source to entry.
StepItemDetail
SourceReclamation Transformers 2005Government work, clause 2.5 and 9.4.10
Data recordequip.liquid-filled-transformers.usbr2005.thermal-agingVerified 2026-10-29
EntryLiquid-filled transformers1 revision
Subject
Liquid-filled transformers (Equipment classes)
Kind
Value in context
Source
Reclamation Transformers 2005, April 2005 edition, clause 2.5 and 9.4.10, page 13 and 193, Transformers: Basics, Maintenance, and Diagnostics, Bureau of Reclamation. Agency document. Agency copy of Reclamation Transformers 2005Agency information page
Also stated in
  • The current standard states life halves for each 8 °C of temperature rise (section 2.5); for an operating temperature increase of 8 to 10 °C (section 9.4.10) (Reclamation Transformers 2005). FIST 3-30 (October 2000) stated operation at only 10 °C above the transformer rating cuts transformer life by 50 percent; the current standard governs.
    Read the reference passage

    3. Transformer Cooling Methods

    "Heat is one of the most common destroyers of transformers. Operation at only 10 °C above the transformer rating will cut transformer life by 50%. Heat is caused by internal losses due to loading, high ambient temperature, and solar radiation."

    FIST 3-30, section 3, page 1, October 2000. Agency copy of FIST 3-30

    The current standard governs; this passage is a public-domain description of the practice dated October 2000.

  • Source passage: Reclamation Transformers 2005, section 2.5, page 13 (April 2005).
    Read the reference passage

    2.5 Core Losses

    "High temperatures in a transformer will drastically shorten the life of insulating materials used in the windings and structures. For every 8 degrees Celsius (°C) temperature rise, life of the transformer is cut by one-half; therefore, maintenance of cooling systems is critical."

    Reclamation Transformers 2005, section 2.5, page 13, April 2005. Agency copy of Reclamation Transformers 2005

    The current standard governs; this passage is a public-domain description of the practice dated April 2005.

  • Source passage: Reclamation Transformers 2005, section 9.4.10, page 193 (April 2005).
    Read the reference passage

    9.4.10 IR for Radiators and Cooling Systems

    "Do not allow a transformer to operate with reduced cooling which drastically shortens transformer life. Remember, an increased operating temperature of only 8 to 10 °C will reduce transformer life by one-half."

    Reclamation Transformers 2005, section 9.4.10, page 193, April 2005. Agency copy of Reclamation Transformers 2005

    The current standard governs; this passage is a public-domain description of the practice dated April 2005.

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equip.liquid-filled-transformers.definition

History

Every recorded change to this data record, oldest first.
DateChange
2026-10-29created

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Cite the governing standard for the fact itself; cite this page as the finding aid.

"Data record equip.liquid-filled-transformers.usbr2005.thermal-aging." Transformer Testing Reference. 2026-10-29. https://www.transformertestingreference.com/data/equip.liquid-filled-transformers.usbr2005.thermal-aging/.