The Engineering Applied Research Of Shunt Capacitor Bank Protection With Suppressing Inrush Transient Current

Along with the rapid development of the national economy in our country, the electrical loads increase substantially and the power network expand rapidly in urban and rural area. It will be a great of significance to reduce the electric power loss and to improve the voltage quality in the enterprise. Currently in the nation-wide, the shunt capacitor bank is used for reactive compensate in most transformer substation because of its economy and convenient maintenance. Because of the changeable load and the profuse harmonic in the factories, especially in the metallurgical works, the shunt capacitor bank is easy to be mangled by the inrush transient current and harmonic current. Therefore, in order to ensure the safety of shunt capacitor bank, it's necessary to research and analyze the transient characteristic of the running shunt capacitor bank.Protection control measures are discussed based on capacitor compensation system of transformer station of Chongqing Iron and Steel Company. After discussing the theory of primary and secondary circuit electric protection of shunt capacitor bank, the effect of electric protection and suppressing method for inrush transient current is demonstrated especially. Firstly the value of inrush transient current of shunt capacitor bank is analyzed by dynamic circuit and shunt capacitor bank theory. Associated with the theory of suppressing harmonic and inrush transient current and the fact that quintuple and below harmonics are abundant, such engineering applications are studied: The optimal capacity of series reactor is calculated by adopting the method of calculating natural vibration resonant point. And then the protection setting value of shunt capacitor bank is set according to operating failure. PLC is used to realize the control device function in order to automatically on/off.Microcomputer protecting equipments are used for the sake of high sensitivity and reliability. Protection and control measures are discussed. And then, it analyses the full-wave Fourier algorithm systematically . A harmonic criterion is raised for protective output based on field data and related engineering data. It not only releases the effect of inrush transient current upon protection, but also recognizes the four statuses—switching on charge, switching on failure, normal after switching on, operating failure exactly.Finally, the protection modification of shunt capacitor's design, type, installation and debugging are analyzed in details from theoretical,technical and economical feasibility. The technical effect is analyzed after modification and the features and experiences of protective measures are generalized.