As of my last knowledge update in September 2021, the term "transformer short-circuit withstand capability" generally refers to the ability of a transformer to withstand the mechanical, thermal, and electrical stresses that occur during a short-circuit fault. In an electrical power system, a short-circuit fault can happen when there's an unintended low-resistance connection between two points of different electrical potential. This can result in a very high current flowing through the system.
During a short-circuit fault, the transformer is subjected to various stresses that can potentially damage it or cause it to malfunction. These stresses include:
Mechanical Stress: The sudden and high electromagnetic forces generated by the short-circuit current can lead to mechanical movement and vibrations within the transformer's windings, core, and other components.
Thermal Stress: The high current flowing through the transformer's windings generates heat due to the resistance of the windings. This rapid increase in temperature can lead to thermal stresses and potentially cause insulation damage or even a fire.
Electrical Stress: The excessive current and the resulting voltage drop across the transformer's impedance can cause electrical stresses on the winding insulation, potentially leading to insulation breakdown.
Transformers are designed with certain short-circuit withstand capabilities to ensure that they can safely handle these stresses without sustaining significant damage. These capabilities are determined during the design phase of the transformer and are influenced by factors such as the transformer's construction, core material, winding configuration, insulation system, and the specific requirements of the electrical system it will be a part of.
It's important for transformers to have a sufficiently high short-circuit withstand capability to prevent catastrophic failures, ensure safety, and maintain the reliability of the power system. Engineers and manufacturers take these considerations into account when designing and specifying transformers for different applications and environments.
Please note that advancements in technology and standards may have occurred after my last update in September 2021, so I recommend checking more recent sources for the latest information on this topic.