配电网中电压互感器消谐、单相消弧和单相永久性故障切线问题的解决方案

我国配电网的中性点不接地,需要抑制频繁发生的电压互感器谐振、设置消弧线圈以及处理永久性单相接地后的自动切线问题,因而叙述了解决以上3个问题的新方案。首先,将三相电压互感器的中性点通过常闭开关接地,谐振时跳开,随后闭合,谐振立即消除,并恢复互感器的正常运行状态。其次,在母线上设置常开的分相动作的三相接地开关,弧光接地时,故障相(根据最高对地电压的相别判定)的上述接地开关闭合,由于母线地网电阻远小于故障点电阻,故障电流被充分分流,恢复电压又极小,因而电弧顺利熄灭,随后跳开接地开关。最后,在永久性单相接地时,先将上述先闭合的故障相的接地开关跳开,并将三相接地开关中某一非故障相的开关接地,造成异地两相接地,故障线路就因单相过流而切除,随后跳开接地开关。总的说来,只用1个单相开关和1个三相开关,配以简单的控制环节即可抑制配网中电压互感器的谐振,从而使单相电弧接地和故障线切除,动作简单可靠,并能带来明显的经济效益。

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.