Tripping Model Of Low Voltage Release Based On Voltage Sag And Its Application In Dongguan Power Grid

Voltage sags currently has become the primary power quality problems faced by many developed countries. With the development of our national economy, its importance is growing rapidly. Low voltage circuit breakers of the release(hereinafter referred to as the low voltage release) is very sensitive to voltage sags. When the voltage sag occurs, low voltage release operates in 10 ms. After the operation, the power supply company usually cannot know the outage until customers call complaints, and the reclosing is a heavy workload. This lengthy process not only causes serious economic losses of customers, but also causes a greater impact on reliability of power supply companies(outage time, time to restore power supply, etc.).Thesis work carried out in Dongguan power grid, by researching and analyzing the two large-scale voltage sag events of Dongguan. And then the mainstream low voltage release and its operating characteristics of Dongguan were researched and analyzed.The test results show that there exists action area, no action area and fuzzy area. On the basis of extensive test results, the voltage tolerance curves of low voltage release are drawn and the tripping model of low voltage release’s sensitivity to voltage sag is established. Finally, the load loss under voltage sags was studied, the modeling ideas based on the types of low voltage release and users’ electricity properities were respectively discussed, and the paper choosed the latter to build the tripping characteristic model of load in Dongguan power grid. According to different users’ s demand on low voltage releases, combined the voltage tolerance curves of low voltage releases, the relationship between load loss and voltage magnitude were fitting. Based on the relative data of voltage sag events, the optimal curves of tripping load which suitable for Dongguan power grid can be obtained. The example shows that this model could reflect the load loss under voltage sags in substation. The research in this paper helps to prevent the voltage sag caused massive load shedding phenomenon of power grid, which can greatly improve the power supply reliability and reduce the customer average interruption time. And then the security, stability and economy of Dongguan power grid will be improved.