Single-phase-fault Line Detection For Non-Solidly Earthed Network

Due to its superiority in the safeguarding of maintenance staff's safety, over-voltage level, insulation of equipment and economy, the approach of non-solid grounded electric network has been widely applied in our country's low & medium voltage level electric grids. Relevant studies have been conducted for the past 50 years and have produced a number of theoretical results as well as devices. Yet up to now no satisfying protection device with a high accuracy of fault-line selection have been achieved. As a result the actual application of those devices has not been popularized. The reason lies in the fact that the theories upon which these devices are established have their limitation, which is that the actual conditions cannot meet the desired requirements for the employment level of these devices. Nowadays 70% of failures with medium & low voltage level grids reside with single-phase grounding. Therefore to develop a protection device with a high accuracy rate of fault-line selection has important theoretical and practical value. Here we propose a fault-line selection approach of zero-sequence transient component of the fault current, which constitutes a complete protection for non-solid grounded electric network along with an assistant method of detecting the direction of the active component of the zero sequence current. Because of the extensive limit to response time, we have developed a comprehensive method by taking use of neural network based on our achievement of default-line selection. This method will make up for the shortcoming of low accuracy rate of single-phase-grounding line selection founded on single arithmetic or principles, which will be better accommodated to the changes of field conditions, compare various arithmetic, identify suitable field conditions and thus generate an easily upgradable and more intelligent system.The accomplishment and marketability of this subject is reasonably complex. Yet we are convinced that it will give momentum to the future developments in this research field.