IEC/TR 61916:2009 provides recommendations and test requirements applicable to electrical accessories. It aims to harmonize general rules for the preparation of international standards in this field. It gives to that effect recommendations which are intended to be used as a guide. The second edition cancels and replaces the first edition published in 1998 and constitutes a technical revision. The main technical changes with regard to the previous edition are as follows: - Updated reference standards. - Introduction of appropriate dimensioning of insulation distances criteria. - Interpretation on glow wire test. - Indication of standard conditions for operation in service. - Modification of Clauses 6 and 7 by including an explanatory introduction concerning how to apply the relevant tests and a simple reference to the horizontal standard. - Modification of Clause 12: Tolerances.