Influence of the Single-Phase Fault Passing Resistance on the Shunt Breaker Technical Efficiency

In the paper, the authors present the influence of the passing resistance at the location of the single-phase fault on the technical efficiency of the shunt breaker, a situation in which, even if the fault is very close to the power transformer station but has a certain fault resistance, lower or higher, the shunt fulfills its functional role of extinguishing the electric arc at the site of the single-phase fault. Also, the results of a “live” earthing test are briefly presented, which confirms the fact that the shunt breaker is not effective at faults very close to the medium voltage bus that is in operation, for an earthing by firmly tying the of a phase at the earth socket of the first pole next to the power transformer station, but in actual / usual operating conditions, when the conductor falls freely on the ground at the same pole, the connected shunt breaker leads to a current through the fault site much smaller than 10 A, and if the defect is transient, it extinguishes itself. At the end, the conclusions highlight the advantages and disadvantages of using the shunt breaker associated with treating the neutral of the medium voltage network through a resistor (R), and the influence of the transition resistance at the single-phase fault site on the technical efficiency of the shunt.