IEEE Std C57.12.91-2020 PDF

Full title and description

IEEE Std C57.12.91-2020 — IEEE Standard Test Code for Dry‑Type Distribution and Power Transformers. This standard provides test methods and procedures used to perform the tests called out in IEEE Std C57.12.01 and other referenced documents, intended as a uniform test code and basis for performance and proper testing of dry‑type distribution and power transformers.

Abstract

This revision (designated 2020) updates test procedures for dry‑type distribution and power transformers to reflect current practice. It modifies several clauses of the earlier edition and adds an Annex to assist in converting test results between 60 Hz and 50 Hz systems. The standard addresses test methods (routine, type and special tests), measurement techniques, and reporting requirements; it does not itself set specific acceptance criteria for transformer performance, which are found in product specifications and companion standards (for example, IEEE Std C57.12.01).

General information

• Status: Active standard (current edition).
• Publication date: Designated 2020 edition; IEEE board approval 24 September 2020; published 28 January 2021.
• Publisher: IEEE / IEEE Standards Association (Institute of Electrical and Electronics Engineers).
• ICS / categories: Electrical equipment — Transformers and reactors (commonly classified under ICS 29.180 / transformer standards).
• Edition / version: 2020 edition (IEEE Std C57.12.91-2020).
• Number of pages: 102 pages (PDF/print edition typical page count).

Scope

The standard describes methods for performing tests applicable to dry‑type distribution and power transformers with the highest voltage winding rated at approximately 601 V or higher. It is intended as a test code (methods and procedures) and applies to all dry‑type transformers, including those with solid‑cast or resin‑encapsulated windings, except where explicitly excluded (for example: instrument transformers; step‑voltage and induction voltage regulators; arc‑furnace transformers; rectifier transformers; specialty and general‑purpose transformers; mine transformers; test and welding transformers; drive and inverter transformers). It is not a specification of design acceptance limits, which remain the purview of companion standards and purchaser requirements.

Key topics and requirements

• Standardized procedures for routine, type, and special tests on dry‑type distribution and power transformers.
• Methods for resistance, ratio, polarity and phase relation tests, no‑load loss and excitation current, impedance and load loss, dielectric tests, temperature testing, short‑circuit tests, and audible sound measurements.
• Updated test procedures and instruments to reflect modern practice (substantive clause changes in this revision compared with the 2011 edition).
• Annex providing guidance for converting test results between 60 Hz and 50 Hz systems (useful for international testing comparisons).
• Requirements for test reporting, calculation of derived data, and certified test data formats for manufacturer and purchaser records.

Typical use and users

Used by transformer manufacturers, independent test laboratories, utilities, consulting engineers, acceptance and quality teams, and procurement/specification authors to define and perform consistent test procedures on dry‑type distribution and power transformers. Also referenced by standards writers and regulatory bodies when harmonizing test requirements or establishing procurement test plans.

Related standards

Commonly used with IEEE Std C57.12.01 (General Requirements for Dry‑Type Distribution and Power Transformers), IEEE C57.12.60 (Thermal Evaluation of Insulation Systems for Dry‑Type Transformers), IEEE C57.12.70 (Terminal Markings and Connections), and other C57 series standards that define performance, construction and acceptance criteria for transformers.

Keywords

dry‑type transformer; distribution transformer; power transformer; test code; test procedures; routine test; type test; dielectric test; temperature test; impedance; loss measurement; IEEE C57.12.91; 50 Hz; 60 Hz conversion.

FAQ

Q: What is this standard?

A: IEEE Std C57.12.91-2020 is the IEEE Standard Test Code for Dry‑Type Distribution and Power Transformers — a test methods document that specifies how to perform and report tests for dry‑type transformers.

Q: What does it cover?

A: It covers test procedures (routine, type and special tests) and measurement methods for dry‑type distribution and power transformers (highest voltage winding approximately 601 V or higher), including electrical, dielectric, thermal and audible tests, plus test reporting and calculation practices. It does not set product acceptance limits, which are provided in companion standards or purchaser specifications.

Q: Who typically uses it?

A: Transformer manufacturers, test laboratories, utilities, engineers specifying acceptance tests, quality and commissioning teams, and standards committees use this test code to ensure consistency and reproducibility of transformer test data.

Q: Is it current or superseded?

A: The 2020 edition (designated IEEE Std C57.12.91-2020) is the active revision, which supersedes IEEE Std C57.12.91‑2011. The IEEE Standards Association records show board approval on 24 September 2020 and publication (IEEE webstore listing) on 28 January 2021.

Q: Is it part of a series?

A: Yes — it is part of the IEEE C57.x family of transformer standards (general requirements, test codes and guides for liquid‑filled and dry‑type distribution and power transformers) and is normally used alongside IEEE Std C57.12.01 and other C57 series documents.

Q: What are the key keywords?

A: Dry‑type transformer, distribution transformer, power transformer, test code, test procedures, IEEE C57.12.91, dielectric test, temperature test, impedance, loss measurement, 50 Hz / 60 Hz conversion.