IEC 61000-4-12:2017 relates to the immunity requirements and test methods for electrical and electronic equipment, under operational conditions, to ring waves occurring in low-voltage power, control and signal lines supplied by public and non-public networks.The object of this document is to establish a common reference for evaluating the immunity of electrical and electronic equipment when subjected to ring waves. The test method documented in this part of IEC 61000 describes a consistent method to assess the immunity of an equipment or system against a defined phenomenon.It has the status of a basic EMC publication in accordance with IEC Guide 107.This edition includes the following significant technical changes with respect to the previous edition:a) addition of a mathematical modelling of ring wave waveform;b) new Annex B on selection of generators and test levels;c) new Annex C on explanatory notes;d) new Annex D on measurement uncertainty;e) addition of high speed CDN;f)A addition of a calibration procedure for CDN.