IEC 61558-1:2017 is also available as IEC 61558-1:2017 RLV which contains the International Standard and its Redline version, showing all changes of the technical content compared to the previous edition.

IEC 61558-1:2017 deals with safety aspects of transformers, reactors, power supply units and combinations thereof such as electrical, thermal and mechanical safety. This document covers the following independent or associated stationary or portable types of dry-type transformers, power supply units, including switch mode power supply units, reactors and combinations thereof in the field of safety. The windings can be encapsulated or non-encapsulated. They are not forming a part of the distribution network. This third edition cancels and replaces the second edition published in 2005 and Amendment 1:2009. This edition constitutes a technical revision. This edition includes the following significant technical changes with respect to the previous edition:
a. fully insulated winding wires (FIW), new tables and aging tests for FIW constructions,
b. overvoltage categories 1, 2, 3 and 4 for clearances and dielectric strength tests (new tables) are included,
c. development of new symbols for the different overvoltage categories,
d. symbol for maximum altitudes, if higher than 2 000 m,
e. symbol for plug in power supply units, if the pins are damaged (tumbling barrel test),
f. symbol for minimum temperature (even during the transportation),
g. alternative temperature measurement, simulated load and back to back method according to IEC 60076-11,
h. short circuit and overload protection, simulated load and back to back method according to IEC 60076-11,
i. adjustment of temperatures in Table 2 according to CENELEC Guide 29,
j. establishing partial discharge test above 750 V for FIW constructions,
k. requirements for toroidal core constructions, division for basic and for supplementary isolation,
l. modification of protection indexes for enclosures (IP-code),
m. dimensioning of rectangular cross section connectors for transformers,
n. repetition test, 80% of required dielectric strength test voltage of Table 14,a.
o. vibration test for vehicles and railway applications,
p. two Y1 Capacitors for working voltages above 250 V and not exceeding 500 V with overvoltage category 3.
It has the status of a group safety publication in accordance with IEC Guide 104.