ABSTRACT
This chapter offers an alternative variant of a very simple and low-priced high-speed overcurrent relay with an algorithm based on the measurement of instantaneous value of a current. In an actual emergency mode, the single protective relay must disconnect not just one but also several common bases simultaneously. The input relay transformer—an interface between the highly sensitive electronic module and the high-current circuit—transforms the useful signal as well as the noise. The use of the new generation of the relays would allow sparing considerable financial expenses connected with the necessity of purchasing the expensive microprocessor-based protective devices. Analysis of the trends in relay technology development shows that the major relay developers do not share a solid and consistent direction for simple current relay design improvement. An addition of an auxiliary relay with a low impedance current coil and a spark-protected power reed switch may be used for energizing external electromechanical relays of automatic or signal systems.
