Ramazon Abdullozoda

Annotation:

The paper is devoted to the assessment of reliability indicators of relay protection operation against single-phase-to-ground faults in 6–10 kV electrical networks. The object of the study comprises outgoing feeders of the “Mirob” 35/6 kV and “Hamадoni” 35/10 kV substations, which are operated by the branch of JSC “Distribution Electric Networks” in the city of Kulob. The initial five-year statistical data were obtained from handwritten documents, namely operational logs of the considered substations. The reliability of the data is confirmed by the fact that the logs are bound, numbered, and certified by the signatures of responsible personnel and the official seal of the organization. The following indicators were determined: the number of correct operations, the total number of single-phase-to-ground faults, the number of false operations, and the number of protection failures. Using established methodologies, the reliability of correct and incorrect operation, as well as the probability of failure-free operation of the considered protections, were calculated. The analysis identified the least reliable protections as well as those with the highest probability of failure-free operation.

Keywords: earth faults, selectivity, reliability, probability of failure-free operation, false tripping.