New methods of suppressing potential transformer resonance, single-phase arc grounding and fault-line breaking in distribution networks

It is necessary to suppress frequent ferro-resonance resulting from potential transformer (TV), to install arc-extinguishing coil, and to resolve the problem of automatic grounded line opening. We put forward new methods to address these three aspects. Firstly, a normal grounding breaker is connected to the neutral of a TV, and it will become open and then close successively when resonance occurs, leading to immediate suppression of the resonance. Secondly, a normal opening three-phase breaker is connected between the bus-bar of a substation and its grounding net. When arcing ground appears on one of outgoing lines, such a breaker of the fault phase will be closed to shunt the arcing path. Consequently, the current and recovery voltage of the fault canal will be substantially suppressed and then the arc canal is extinguished. Finally, when a permanent single-phase fault occurs, an attached breaker of sound phases will be closed after the opening of the breaker of the former grounded phase. Therefore, an inter-phase short circuit appears between two different locations; and the single-phase over-current passing through the grounded line makes the breaker open immediately. In summary, for the purpose of TV resonance suppression, single-phase arc grounding, and fault-line breaking in distribution networks, it is sufficient to use only one single-phase breaker and one three-phase breaker in a substation with simple control devices, showing potentially significant economic benefits.