IEC 60137:2017

Overview

IEC 60137:2017 - Insulated bushings for alternating voltages above 1 000 V - is the International Electrotechnical Commission standard that specifies characteristics, ratings and test requirements for insulated bushings intended for electrical apparatus (transformers, switchgear, machines and installations) in three‑phase AC systems with highest voltage for equipment above 1 000 V and power frequencies from 15 Hz to 60 Hz. This edition (7.0, including the May 2018 corrigendum) introduces technical updates such as the inclusion of resin‑impregnated synthetic (RIS) bushings, revised altitude correction, temperature‑rise testing for liquid‑insulated bushings, routine dry lightning impulse testing for transformer bushings (Um > 72.5 kV) and discussion of Very Fast Transient (VFT) effects.

Key topics and technical requirements

• Scope and ratings: definition of rated highest voltage (Um), rated current, thermal short‑time and dynamic currents, creepage distances and temperature limits.
• Test classification: clear separation of type tests, routine tests and special tests with acceptance criteria.
• Dielectric tests: dry/wet power‑frequency withstand, long‑duration (ACLD), switching and lightning impulse (BIL/SIL) tests.
• Thermal and mechanical tests: temperature‑rise testing, thermal stability, cantilever load and verification of short‑time thermal current withstand.
• Sealing and pressure tests: tightness and internal/external pressure tests for liquid‑filled, gas‑filled and compound bushings.
• Electrical integrity: partial discharge measurement, dissipation factor (tan δ) and EMC (emission/immunity) testing.
• New/updated elements: RIS materials, additional Um values (including Um ≤ 1,1 kV (1.1 kV) and higher Um values introduced in this edition), altitude correction (>1 000 m) and VFT guidance.

Practical applications

IEC 60137 provides the technical framework to:

• Design and qualify transformer bushings, reactor and switchgear bushings.
• Ensure factory acceptance and site testing for insulated bushings used in power transmission and distribution.
• Validate sealing, mechanical strength and dielectric performance for liquid‑, gas‑ and solid‑insulated bushings.
• Support procurement specifications and contractual agreements between suppliers and purchasers (special application cases such as DC systems, capacitor bushings or non‑three‑phase systems may be covered by agreement).

Who uses IEC 60137

• Bushing and transformer manufacturers
• Independent test laboratories and certification bodies
• Power utilities and transmission system operators
• Switchgear and substation equipment designers
• Procurement engineers and standards compliance officers

Related standards

IEC 60137 references other IEC normative documents covering materials, measurement methods and related test procedures. Users should consult the standard’s normative references for complementary standards on partial discharge, EMC and dielectric testing.