Analysis And Optimization Of Relay Protection System For Rod Power Supply In Nuclear Power Plant

The task of power supply system for control rod drive mechanism in nuclear power plant is to provide stable and reliable power supply for control rod drive mechanism.Although there are some technical specifications for relay protection configuration and calculation of electrical main equipment at home and abroad,the research on relay protection system of control rod power supply in nuclear power plant is not perfect,and there is no systematic analysis on the whole rod power supply units.As a result,the protection setting coordination between the two units of rod power supply system is not appropriate.When the relay protection device acts,it may cause the protection malfunction,resulting in the trip of the whole rod power supply units,and eventually the reactor rod dropping and shutdown.In this paper,the working principle of rod power supply system is introduced firstly.Taking the control rod drive power supply system of 100 k W second and third generation pressurized water reactor nuclear power plants as the research object,the corresponding overall scheme of relay protection is proposed.This paper focuses on the research on the loss of excitation fault of rod power supply.In order to explore the change of the terminal current of the other without loss of excitation under the condition of loss of excitation of one unit in parallel operation,the double loss of excitation fault circuit model of rod power supply unit and the simulation model of MATLAB / Simulink rod power supply are established.Finally,the structure of loss of excitation protection based on admittance measurement criterion is proposed.This paper also studies the coordination between the loss of excitation protection and the low excitation limiter of the rod power supply,puts forward the coordination scheme of the loss of excitation protection and the low excitation limiter based on the admittance plane,and verifies it;The coordination between loss of excitation protection and inverse time over-current protection is mainly studied.The coordination scheme between loss of excitation protection and inverse time over-current protection is proposed,and the action time of loss of excitation protection and inverse time over-current protection is verified.Finally,an experimental prototype of self-shunt brushless excitation mode rod power supply system is built,and the simulation model is verified.The proposed scheme of loss of excitation protection and low excitation limiter protection,loss of excitation protection and inverse time over-current protection is verified by experiments.The results show that the proposed scheme can meet the coordination principle and verify the correctness of the proposed scheme.