ABSTRACT
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. Many of the mistakes and inaccuracies found in the IEC standards discussed in this chapter are dangerous symptoms indicating a very low quality of international standards and a high hazard in their practical usage, in particular for Digital protection relays (DPR) design and improvement. Electromechanical relays are the major elements of each DPR and are also used in non-microprocessor-based constructions. The electromagnetic compatibility of power equipment is determined completely by the solid-state relay only. Generally, any electric relay has an input-sensing element that responds upon an input value, and an output element that performs the switching in an external circuit.
