ABSTRACT
In old electromechanical protective relays as an element-switching trip coil of a high-voltage circuit breaker, one used a special embedded auxiliary latching relay, with manual resetting and with an embed flag indicating the relay condition. The wide usage of nonsuitable electromechanical relays in practically all types of Digital protection relays, and also in the microprocessor-based devices providing communication between the protective relays and in other analogous devices which are available in the market. Transient resistance of contacts increases, and so does their temperature. In miniature relays, this leads to the fusion of the plastic case near contacts, contamination of contacts, and further growth of transient resistance. The maximum number of actuations of these relays during their entire service life hardly exceeds several thousand. An analysis of the standards’ requirements for the testing of relay insulation and withstanding voltage also evokes bewilderment. For example, in International Electrotechnical Commission 60947-5-1 the list of relay parts is given with the test voltage attached.
