Distance Protection Controi Strategy Study To Prevent Cascading Trips Based On Related Area

The distance protection control strategy to prevent cascading trips based on related area can effectively identify the flow transfer happening in the power grid. Coping with the effects of the flow transfer from both backup protection and overload control, this strategy can reliably prevent cascading trips. As a result, this method is of great importance for practical significance in the prevention of large-scale blackout in the power system. Based on the analysis of the characteristics and shortcomings of the existing methods, the control strategy which associates the backup protection setting value adjustment with the transmission line overload control to analysis and design, was firstly applied in this paper. By using the wide area information to improve the performance of the traditional distance protection, this method realizes the comprehensive application of three lines defense in the power grid security defense system, and explores the harmonious unity strategy combined with protection and control. The main achievements and contributions of this dissertation are as follows:(1) An overload blocking scheme for zone3distance protection based on the local information was proposed. Given the different discrimination criterion for the failure state and load state, this paper used the criterion to distinguish fault and overload which makes the zone3distance protection own the ability of selective block;(2) An apparent impedance correction algorithm which can identify the change of network structure was proposed. Use the real-time PMU data which synchronize with the power system operation, the dynamic calculation of transmission line apparent impedance change process in flow transfer state is realized. Connect the apparent impedance and the active power, and then identify the flow transfer from the perspective of distance protection;(3) An adaptive setting scheme for distance backup protection was proposed. Raise the overload limit calculation method for zone3distance protection in the different setting value conditions. On the basis of overload limit, raise the adjusting setting scheme within or outside the boundaries of overload limit;(4) A method for related area construction was proposed. By analyzing the flow transfer in the initial limited impact on the power grid, construct a flow transfer area related with backup protection and overload control. Using the related area can simplify the entire network calculation for area calculation;(5) A control strategy to prevent cascading trips based on related area was proposed. This strategy uses the dispatching center as a decision-making central with backup protection adjustment and overloads control strategy, and integrates the protection and control to realize the comprehensive application of three lines of defense in power grid security defense system.