The Influence of Load Low-voltage Releasing on Under-voltage Load Shedding Strategy

With the increasing application of voltage-sensitive load, the problem of load low-voltage releasing in user side is becoming more and more obvious. When faults occur in the system, the relative measures of under-voltage load shedding (UVLS) strategy are used. Meanwhile the phenomenon of load low-voltage releasing in user side will enlarge the total removable load, which leads to such disadvantages as the removal of the excessive amounts of loads and the very high recovery voltages. In this paper, through the study of the low-voltage releasing characteristics of some typical loads in grid side, the composite load model is built by considering the characteristics of load low-voltage releasing firstly. Then the mechanism of the influence of low-voltage releasing on the load under-voltage shedding measures by the load low-voltage release is analyzed. A simulation of 10-machine39-bus system is used to verify them. The study is analyzed. Through the simulation on a 10-machine 39-bus system, the impact of low-voltage releasing on under-voltage load shedding is analyzed. Results show that such three factors as the amount of load low-voltage releasing in user side, whether happening or not of the low-voltage release and relative delay release time, will influence the under-voltage load shedding strategy.