IEEE Std C57.110-2018 PDF

Full title and description

IEEE Std C57.110-2018 — IEEE Recommended Practice for Establishing Liquid‑Immersed and Dry‑Type Power and Distribution Transformer Capability when Supplying Nonsinusoidal Load Currents. This recommended practice provides calculation methods, application guidance and illustrative examples to evaluate and specify two‑winding liquid‑immersed and dry‑type transformers expected to carry loads that include nonsinusoidal (harmonic) currents; suggested temperature‑rise calculation methods and comparison annexes are included.

Abstract

Revision standard (2018) that establishes uniform, conservative methods for determining the capability of existing or new liquid‑immersed and dry‑type power and distribution transformers to supply nonsinusoidal load currents without loss of normal life expectancy. The document contains two general calculation approaches, worked examples, annex comparisons to other industry methods, and recommended temperature‑rise evaluation procedures.

General information

• Status: Active Standard.
• Publication date: October 31, 2018.
• Publisher: IEEE (Power & Energy Society / IEEE Standards Association).
• ICS / categories: 29.180 — Transformers, Reactors.
• Edition / version: 2018 (supersedes IEEE C57.110‑2008).
• Number of pages: 68 pages (electronic PDF edition).

Scope

This recommended practice applies only to two‑winding power and distribution transformers covered by IEEE Std C57.12.00, IEEE Std C57.12.01 and NEMA ST20.1. It provides calculation methods to conservatively evaluate the feasibility of an existing installed dry‑type or liquid‑immersed transformer to supply nonsinusoidal load currents as part of the total load, and gives application information to assist in properly specifying a new transformer expected to carry nonsinusoidal loads. It does not apply to rectifier transformers.

Key topics and requirements

• Methods to quantify transformer capability under nonsinusoidal (harmonic) load currents, including conservative calculation procedures.
• Harmonic loss factors and k‑factor style considerations for assessing additional heating and losses due to current distortion.
• Two calculation approaches: one for users with detailed loss‑density/distribution data and a simplified approach for cases with only certified test report data.
• Recommended temperature‑rise calculation methods and guidance on hottest‑spot and average winding temperature effects.
• Application guidance for specifying new transformers expected to supply nonsinusoidal loads (information to provide to manufacturers).
• Worked examples and annexes comparing the standard’s calculations with other industry methods to aid correct application.
• Explicit exclusion of rectifier transformers from the practice (scope limitation).

Typical use and users

Used by transformer designers, manufacturers, electrical utilities, consulting engineers, industrial plant electrical engineers and asset managers who must assess or specify transformer capability where loads include nonlinear equipment (variable‑frequency drives, rectifiers, UPS systems, power electronics) that introduce harmonic currents. The standard supports both assessment of in‑service equipment and specification of new transformers for harmonic‑rich installations.

Related standards

Commonly used alongside IEEE Std C57.12.00 (general requirements for liquid‑immersed transformers), IEEE Std C57.12.01 (general requirements for dry‑type transformers), and NEMA ST20.1. It replaces IEEE C57.110‑2008 and is part of the IEEE C57 family of transformer guides and standards (see also relevant C57.x guides for losses, through‑fault duration and oil maintenance).

Keywords

nonsinusoidal currents, harmonics, harmonic loss factor, k‑factor, transformer loading, temperature rise, hottest‑spot, two‑winding transformers, liquid‑immersed, dry‑type, transformer capability.

FAQ

Q: What is this standard?

A: IEEE Std C57.110‑2018 is a recommended practice that provides calculation methods and guidance for evaluating and specifying two‑winding liquid‑immersed and dry‑type power and distribution transformers when part of the load current is nonsinusoidal (contains harmonics). It sets out conservative methods to ensure transformer life expectancy is not unduly reduced by harmonic heating.

Q: What does it cover?

A: It covers methods to calculate additional losses and temperature rise due to nonsinusoidal currents, guidance for specifying transformers for harmonic‑rich loads, worked examples, and annexes comparing its calculations to other industry approaches. The practice applies only to two‑winding transformers described in IEEE C57.12.00 and C57.12.01 and excludes rectifier transformers.

Q: Who typically uses it?

A: Transformer design engineers, utility engineers, consulting and plant engineers, manufacturers and asset managers—anyone who must assess in‑service transformer capability under harmonic loads or specify new transformers for installations containing nonlinear loads such as drives, UPSs and power electronics.

Q: Is it current or superseded?

A: As published on October 31, 2018, IEEE C57.110‑2018 is an active recommended practice and supersedes IEEE C57.110‑2008. A revision project (PC57.110) with a PAR to revise/supersede C57.110‑2018 was approved by IEEE on February 12, 2026; that project indicates an update is in progress but, as of February 26, 2026, the 2018 edition remains the published active practice until any new edition is issued.

Q: Is it part of a series?

A: Yes — it is part of the IEEE C57 family of transformer standards and guides (general requirements, loss and loading guides, through‑fault guides, oil maintenance, etc.). It is specifically referenced with IEEE C57.12.00 and C57.12.01 and is intended to be used in conjunction with other C57 documents when specifying or assessing transformers.

Q: What are the key keywords?

A: Nonsinusoidal currents, harmonics, harmonic loss factor, k‑factor, transformer loading, temperature rise, hottest‑spot, two‑winding transformers, liquid‑immersed, dry‑type.