IEC 60555-3 specifies limits for the voltage fluctuations that may be produced by an individual appliance and gives methods of test and calculation. The purpose of this report is to explain the way in which the limits and test methods were developed so as to help understanding of the standard and the way in which it should be used. After reviewing the need for voltage fluctuation limits, the background to each of the clauses in the standard is presented. This publication has the status of a report.