IEC 62631-3-4:2019 covers procedures for the determination of insulation resistance and volume resistivity of insulating materials by applying DC-voltage and temperatures up to 800 °C. The typical application materials include high temperature mica plate and alumina ceramics.
This edition of IEC 62631-3-4 cancels and replaces IEC 60345 "Method of test for electrical resistance and resistivity of insulating materials at elevated temperatures", published in 1971. This edition constitutes a technical revision.
This edition includes the following significant technical changes with respect to IEC 60345:

1. The revised standard becomes part of the series IEC 62631-3-x. Title of the standard is changed and adapted to the series as Part 3-4.
2. Clauses 2 "Normative references", 3 "Terms and definitions", and 4 "Significance" are added.
3. Subclauses 5.2 "Power supply, Voltage", 5.3.1.2 "Number of test specimens" and 5.3.1.3 "Conditioning and pre-treatment of test specimens" are added.
4. In 5.3.5 "Special precautions during measurements", errors analysis in the measurement of current are modified, and aligned with IEC 62631-3-1.
5. In 6.2 "Increasing the temperature by steps (method B)", the method for more than one specimen is removed.
6. The standard atmospheric conditions for testing and conditioning, especially the temperature, are replaced according to IEC 60212.
7. The circuit diagram of test apparatus is modified, and the structure diagram and pictures of test apparatus are added in Annex A.
8. The orders of part clauses are adjusted.