MT 12 - TC 42/MT 12

IEC 62475:2026 is applicable to high-current testing and measurements on both high-voltage and low-voltage equipment. It deals with steady-state and short-time direct current (as e.g. encountered in high-power DC testing), steady-state and short-time alternating current (as e.g. encountered in high-power AC testing), and impulse-current. In general, currents above 100 A are considered in this International Standard, although currents less than this can occur in tests.
This standard:
• defines the terms used;
• defines parameters and their tolerances;
• describes methods to estimate uncertainties of high-current measurements;
• states the requirements applicable to a complete measuring system;
• describes the methods for approving a measuring system and checking its components;
• describes the procedure by which the user shows that a measuring system meets the requirements of this document, including limits set for uncertainty of measurement.
This standard also covers fault detection during, for example, lightning impulse testing.
This second edition cancels and replaces the first edition published in 2010. This edition constitutes a technical revision.
This edition includes the following significant technical changes with respect to the previous edition:
• minor errors in edition 1 have corrected;
• terms and definitions have been modified to achieve best possible adherence to IEC 60060‑2:2025 and have been ascribed appropriate [SOURCE];
• terms and definitions which in edition 1 were presented in clauses other than Clause 3 have been moved into Clause 3.
• Annex B, Clause B.4 has been amended to provide an example of uncertainty calculation for the use of an approved measuring system;
• Clause C.2 has been deleted since the definitions given there are not referred to, with the exception of the origin of the step, which is used in Annex D. The applicable information has been added to Annex D as Note 1.
• Annex G, Clause G.8 has been amended to replace “peak factor” by “a factor”. Texts have been clarified. Equations for relation between factor κ and cos ϕ have been developed to a simplified form.
• Annex G, Clause G.9 has been added.

IEC 62475:2010 is applicable to high-current testing and measurements on both high-voltage and low-voltage equipment. It deals with steady-state and short-time direct current (as e.g. encountered in high-power d.c. testing), steady-state and short-time alternating current (as e.g. encountered in high-power a.c. testing), and impulse-current. In general, currents above 100 A are considered in this International Standard, although currents less than this can occur in tests. This standard also covers fault detection during, for example, lightning impulse testing.

Applies to the construction and use of sphere-gaps for measuring the peak value of alternating, direct and both full standard and longer tail impulse voltages. Peak values of the disruptive voltages in air are given in tabular form. Note: - For high-voltage test techniques, see IEC 60060.