IEC 61557-3:2019 specifies the requirements applicable to equipment for measuring the loop impedance between a line conductor and protective conductor; between a line conductor and neutral; or between two line conductors by using the voltage drop when the circuit under test is loaded. IEC 61557-3:2019 cancels and replaces the second edition published in 2007. This edition constitutes a technical revision. This edition includes the following significant technical changes with respect to the previous edition:
a) addition of equirements as regards the measurement category;
b) addition of new requirements for operating instructions;
c) alignment of the structure with that of the whole IEC 61557 series.