IEEE Std C57.12.38-2014 PDF

Full title and description

IEEE Std C57.12.38-2014 — IEEE Standard for Pad-Mounted-Type, Self-Cooled, Single-Phase Distribution Transformers 250 kVA and Smaller: High Voltage, 34 500 GrdY/19 920 V and Below; Low Voltage, 480/240 V and Below. This product standard specifies certain electrical, dimensional and mechanical characteristics and safety considerations for single‑phase, 60 Hz, mineral‑oil‑immersed, self‑cooled, pad‑mounted, compartmental‑type distribution transformers rated 250 kVA and smaller; it addresses connector, bushing and terminal arrangements for radial or loop feed systems but does not cover the electrical/mechanical requirements of separately supplied accessory devices.

Abstract

This standard establishes uniform technical requirements and dimensional criteria intended to promote interchangeability, safe operation, and reliable field installation of pad‑mounted, self‑cooled single‑phase distribution transformers (≤250 kVA). It includes electrical ratings, insulation levels, mechanical dimensions, and basic safety considerations relevant to underground primary cable systems and pad‑mounted compartmental enclosures.

General information

• Status: Superseded standard (historical; replaced by a later revision of the same designation).
• Publication date: 05 September 2014.
• Publisher: IEEE (Institute of Electrical and Electronics Engineers) / IEEE Standards Association (PES Transformers committee).
• ICS / categories: 29.180 — Transformers. Reactors (electrical engineering classification).
• Edition / version: 2014 edition (IEEE Std C57.12.38-2014), with Corrigendum C57.12.38-2014/Cor 1-2016 issued to correct dimensional detail(s).
• Number of pages: Approximately 31 pages (varies by format/provider).

Scope

The standard applies to pad‑mounted, compartmental, self‑cooled, liquid (mineral oil) immersed single‑phase distribution transformers rated 250 kVA and smaller, for 60 Hz systems. It addresses units with high‑voltage ratings up to 34 500 GrdY/19 920 V and low‑voltage ratings up to 480/240 V (or similar configurations), and covers electrical, dimensional and mechanical characteristics needed for underground primary cable applications and for arrangements of connectors, bushings and terminals for radial or loop feed systems. It explicitly excludes detailed electrical and mechanical specifications for accessory devices that may be supplied with the transformer.

Key topics and requirements

• Ratings and designation: kVA ratings (≤250 kVA), voltage classes (HV up to 34 500 GrdY/19 920 V; LV up to 480/240 V).
• Electrical characteristics: insulation levels, rated currents, vector group/configuration guidance and applicable test considerations.
• Dimensional and mechanical requirements: basic enclosure and pad‑mount dimensional drawings, bushing and connector heights/locations, clearances and mounting details (corrigendum issued to correct a dimensional figure).
• Connector, bushing and terminal arrangements: recommended arrangements for radial and loop feed underground systems, separable connector considerations.
• Cooling and liquid (oil) considerations: self‑cooled, liquid‑filled construction and associated mechanical features for safe operation and servicing.
• Safety and installation considerations: compartmentalization, grounding, access, and instructions intended to promote safe field installation and operation.
• Exclusions: accessory devices supplied with the transformer (their detailed electrical/mechanical requirements are not covered by this standard).

Typical use and users

Primary users are electric utilities, distribution system designers, transformer manufacturers, procurement/specification engineers, testing laboratories, and contractors responsible for underground distribution and pad‑mounted equipment. The standard is used for specifying purchases, designing pad‑mounted transformer installations, and ensuring interchangeability and safe operation in underground distribution networks.

Related standards

Commonly referenced companion and related IEEE standards include: IEEE C57.12.25 (pad‑mounted transformers with separable insulated high‑voltage connectors), IEEE C57.12.00 (general requirements for liquid‑filled distribution transformers), IEEE C57.12.28 and C57.12.29 (bushing and connector standards), IEEE C57.12.90 (test code), IEEE C57.91 (guide for loading), IEEE C57.12.70 (general requirements — terminal markings and nameplates), and industry connector standards such as IEEE 386. Many of these are cited for testing, construction or connector interface requirements.

Keywords

pad‑mounted, padmounted, self‑cooled, single‑phase, distribution transformer, 250 kVA, mineral‑oil‑immersed, compartmental, high voltage 34 500 GrdY/19 920 V, low voltage 480/240 V, bushings, connectors, IEEE C57.12.38.

FAQ

Q: What is this standard?

A: IEEE Std C57.12.38-2014 is a product standard that defines electrical, dimensional and mechanical characteristics and certain safety features for pad‑mounted, self‑cooled, single‑phase distribution transformers rated 250 kVA and smaller.

Q: What does it cover?

A: It covers ratings, insulation and electrical characteristics, dimensional drawings and mechanical construction details, bushing/connector/terminal arrangements for underground primary systems, and general safety/installation considerations. It does not define the detailed electrical/mechanical requirements for separately supplied accessory devices.

Q: Who typically uses it?

A: Utilities, transformer manufacturers, distribution system designers, procurement/specification engineers, testing labs and installation contractors use it when specifying, designing, manufacturing, testing or installing pad‑mounted distribution transformers.

Q: Is it current or superseded?

A: IEEE Std C57.12.38-2014 is a historical/superseded edition. It received a corrigendum (C57.12.38-2014/Cor 1-2016) to correct dimensional detail(s), and the series has since been revised with a later edition (C57.12.38-2025). Users requiring the most current requirements should refer to the latest revision.

Q: Is it part of a series?

A: Yes — it belongs to the IEEE C57.12 family of distribution and pad‑mounted transformer standards and is commonly used alongside other C57.12 documents (for example C57.12.00, C57.12.25, C57.12.28, C57.12.29, C57.12.90, etc.) that cover general requirements, connectors, tests and related topics.

Q: What are the key keywords?

A: Key keywords include: pad‑mounted, padmounted, self‑cooled, single‑phase, distribution transformer, mineral oil, 250 kVA, 34 500 GrdY/19 920 V, 480/240 V, bushings, connectors, IEEE C57.12.38.