nsBAS EN IEC 61557-9:2026

IEC 61557-9:2023 specifies the requirements for the insulation fault location system (IFLS) that localizes insulation faults in any part of the system in unearthed IT AC systems and unearthed IT AC systems with galvanically connected DC circuits having nominal voltages up to 1 000 V AC, as well as in unearthed IT DC systems with voltages up to 1 500 V DC, independent of the measuring principle. IEC 61557-9:2023 cancels and replaces the third edition published in 2014. This edition constitutes a technical revision. This edition includes the following significant technical changes with respect to the previous edition: a) new terms and definitions on maximum admissible locating AC and DC currents and voltages; b) the requirements on locating current and locating voltage have been revised; c) performance requirements have been added; d) the test requirements for locating current and locating voltage have been revised; e) the structure of this document has been adapted to that of IEC 61557-1:2019; f) the limit values under Clause A.2 were adapted to fit the changed test methods in 6.2.3.