NEW! IEC 61921:2017 is available as IEC 61921:2017 RLV which contains the International Standard and its Redline version, showing all changes of the technical content compared to the previous edition.IEC 61921:2017 is applicable to low-voltage AC shunt capacitor banks intended to be used for power factor correction purposes, possibly equipped with a built-in switchgear and controlgear apparatus capable of connecting to or disconnecting from the mains part(s) of the bank with the aim to correct its power factor. Low-voltage power factor correction banks if not otherwise indicated hereinafter and where applicable comply with the requirements of IEC 61439-1 and IEC 61439-2. This second edition cancels and replaces the first edition published in 2003. It constitutes a technical revision. This edition includes the following significant technical changes with respect to the previous edition: numerous changes regarding verification methods to align with IEC 61439-1; modification of marking; add routine verification of rated output; new Annex D with guidance on methods for temperature rise verification; update of normative references; general editorial review. Keywords: low-voltage AC shunt capacitor banks