IEEE Std C57.109-2018 PDF

Full title and description

IEEE Std C57.109-2018 — IEEE Guide for Liquid-Immersed Transformers Through‑Fault‑Current Duration. This guide gives recommendations for coordinating overcurrent protective devices with the through‑fault current withstand characteristics of liquid‑immersed power and distribution transformers; it presents transformer coordination curves for the four transformer categories defined in IEEE Std C57.12.00.

Abstract

Revision standard (2018) that provides guidance to limit transformer exposure time to short‑circuit currents by matching protective device operating characteristics to transformer withstand capability; includes coordination curves for Categories I–IV of liquid‑immersed transformers and recommendations for application of relays and fuses. This guide is not intended to imply overload capability.

General information

• Status: Active Standard.
• Publication date: October 5, 2018 (Board approval 27 September 2018).
• Publisher: Institute of Electrical and Electronics Engineers (IEEE).
• ICS / categories: Electrical engineering — Transformers / Reactors (commonly catalogued under ICS 29.180).
• Edition / version: IEEE Std C57.109-2018 (revision of IEEE Std C57.109-1993).
• Number of pages: 23 pages (published PDF length as listed by IEEE distribution channels; some reseller listings may show minor formatting variations).

Scope

This guide applies to liquid‑immersed transformers referenced in IEEE Std C57.12.00 as Categories I, II, III and IV. It sets forth recommendations essential for selecting and coordinating overcurrent protective devices so transformer exposure to short‑circuit currents is limited to durations the transformer can safely withstand. The scope explicitly excludes implying or defining overload capability.

Key topics and requirements

• Definition and categorization of liquid‑immersed transformers (Categories I–IV) for coordination purposes.
• Transformer through‑fault current duration curves and methodology to relate fault magnitude to allowable duration.
• Guidance on application and coordination of overcurrent protective devices (fuses, relays) with transformer withstand capability.
• Recommended practices for using coordination curves when specifying protective device operating characteristics.
• References to related IEEE standards used for protective device application and transformer requirements.

Typical use and users

Used by power system engineers, transformer designers, utility protection engineers, relay and protection vendors, testing laboratories, and specifiers who must ensure coordination between transformer mechanical/electrical withstand limits and system protective devices. Typical applications include distribution and power transformer protection coordination studies, specification writing, and safety assessments.

Related standards

Commonly referenced standards include IEEE Std C57.12.00 (general requirements and category definitions for liquid‑immersed transformers) and IEEE Std C37.91 (guidance on protecting power transformers). The guide is part of the family of IEEE C57 series standards addressing transformer design, testing, and application.

Keywords

transformer, liquid‑immersed, through‑fault, fault duration, coordination curves, overcurrent protection, relays, fuses, transformer categories, IEEE C57.109.

FAQ

Q: What is this standard?

A: IEEE Std C57.109-2018 is an IEEE guide that provides recommendations for limiting the exposure time of liquid‑immersed transformers to short‑circuit currents by coordinating protective devices with transformer withstand characteristics.

Q: What does it cover?

A: It covers transformer through‑fault current duration curves, methods to relate fault magnitude to allowable duration, and practical guidance for applying and coordinating overcurrent protective devices for liquid‑immersed transformers (Categories I–IV). It does not address overload capability.

Q: Who typically uses it?

A: Power system protection engineers, transformer manufacturers and designers, utility engineers, relay and fuse manufacturers, testing labs, and anyone responsible for specifying or evaluating transformer protection coordination.

Q: Is it current or superseded?

A: As published on October 5, 2018, IEEE Std C57.109-2018 is the current active revision and it supersedes IEEE Std C57.109-1993. Users should check IEEE SA listings for any later revisions or amendments.

Q: Is it part of a series?

A: Yes — it is part of the IEEE C57 family of standards and guides dealing with transformers (design, testing, application and protection), and it cross‑references standards such as IEEE Std C57.12.00 and IEEE Std C37.91.

Q: What are the key keywords?

A: transformer, liquid‑immersed, through‑fault, fault duration, coordination curves, overcurrent protection, relay, fuse, C57.109.