Ning Tong

Single-phase earth fault location method based on harmonic analysis for the NUGS

It has been a hot issue for decades about the faulted feeder selection as well as the fault location methods for the neutral un-effectively grounded distribution network. As for the existing methods dealing with the single-phase earth fault in this kind of network, they show great limit as the impact of the Petersen-coil is usually not taken into consideration, and the zero-sequence current is in most cases not available. In this paper, a novel single-phase earth fault location method making use of the characteristics of harmonic component of faulted phase current is proposed, and a range voting algorithm is designed to decide the fault location. Its validation and superiority is finally assessed under various fault conditions.

Fault identification method based on the neutral point medium resistance switching-on for the distribution network

It has long been a hot issue of the single-phase to ground fault identification technics for the distribution network with neutral un-grounded system (NUS), the neutral resonant grounded system (NES) and the neutral resistor grounded system (NRS). The fault detection and location could be very difficult since the faulted component in above scenarios is less pronounced, and meanwhile it becomes a less helpful by using conventional scheme if the arc suppression coil is equipped. In this paper, a novel method based on the neutral point medium resistance switching-on is introduced, and the faulted component of the lines in the distribution network is analyzed. By the comparison between the variations of the faulted phase-current before and after the medium resistance switching-on, the faulted location can thus be determined. Simulation results indicate that in most cases, the proposed method show great reliability and immune to the changes of the system conditions.

A novel kind of monitoring and analyzing system for digital substation functional loop

Currently, the schedule preparation of condition-based maintenance for the secondary devices in digital substation highly relies on the information supporting of the condition monitoring. In this paper, a novel kind of real-time condition monitoring and analyzing system for the functional loop applied in the digital substation is introduced. Based on the data captured in the network of process level by the collecting unit, an analyzer is equipped in a higher level in order to get the configuration of the digital substation, and furthermore, this virtual linkage of functional loop is displayed and updated on the client as undirected graphs. Using these graphs and with the help of the information in the offline database, this system can offer estimation results for the MTTF of a certain functional loop, which makes contribution to the digital substation condition-based maintenance in real-time.