IEC 61439 is a key international standard for low voltage distribution boxes. This standard gives you a clear framework for safety and reliability. Design requirements help you follow important standards like. ents), and the electrical equipment, formed by the internal connections and by the incoming and outgoing termina is regard, there has been an evolution which has resulted in the replacement of the previous Standard IEC 60439 with the present Stand rd IEC 61439. This is especially true in light of more stringent code enforcement and the current design trend to deliver energy savings by selecting low-impedance transformers. 11 of IEC 61439-1 outlines two critical tests to assess a switchgear panel's ability to withstand short circuit stresses: Icw Test – Tests the busbar system's ability to endure the mechanical forces generated during a fault. For example, a test at 65kA for 3 seconds with a peak of 143kA.