The electromagnetic forces generated during the peak of a fault current can reach hundreds of tonnes in just milliseconds. These forces can bend windings, displace clamping structures, or cause internal collapse. IEC 60076-5 outlines two ways to verify dynamic withstand: A. Direct Short-Circuit Test
is the international standard that defines the requirements for power transformers to withstand the thermal and dynamic effects of external short circuits without sustaining damage. Published by the International Electrotechnical Commission, this document is part of the broader IEC 60076 series , which governs the design, testing, and operation of transformers globally.
The standard applies to both oil-immersed and dry-type power transformers as defined in IEC 60076-1 . Its primary goal is to ensure that a transformer can survive various fault conditions, including: Three-phase short circuits. Line-to-line and line-to-earth faults. Double-earth faults. iec 60076-5
When a short circuit occurs, the current in the windings can increase to many times the rated value. This causes rapid Joule heating.
: The maximum allowable temperature during a fault depends on the insulation class of the materials used (e.g., cellulose paper in oil-immersed units). 3. Dynamic Ability (Mechanical Withstand) The electromagnetic forces generated during the peak of
: The transformer is subjected to a series of short-circuit "shots" at full system voltage.
The standard identifies two distinct modes of failure that the unit must resist: forces and thermal energy. 2. Thermal Ability to Withstand Short Circuit Direct Short-Circuit Test is the international standard that
: Typically, transformers must be designed to withstand these thermal effects for a duration of 2 seconds .