Standards of the International Electrotechnical Commission (IEC) are the major documents affecting international technical policy and also the technical policies of the various countries whose national standards are based on IEC standards. Therefore, any inaccuracy, half-words, or unintelligible formulations in IEC standards can lead to very serious aftereffects. The question arises if the standards in effect today are ideal. We shall try to examine this question on the basis of the critical analysis of some basic standards in the fields related to digital protective relays (DPRs), in particular on electromechanical, solid-state, and reed switch–based relays widely used in existing DPRs and described in this book for perspective models.