Magnetic Field Analysis And Discharge Risk Assessment Of New Generation Large Capacity Synchronous Condenser

The new generation large synchronous condenser is mainly used to adjust the reactive power of HVDC transmission system,and can operate under different conditions of over-excitation,under-excitation and even loss of excitation.The high output reactive power of synchronous condenser will lead to the increase of end leakage flux,and thereby may restrict the operating ability of the synchronous condenser.The increase of the end magnetic density will affect the loss of the end structure and the electromagnetic force of the winding.Long time operation is easy to cause the damage of the end structure and the vibration fracture of the winding,resulting in the shutdown and maintenance of the synchronous condenser.The end axial flux density will easily produce a large induced electromotive force in the stator core spacer,which will increase the discharge risk and reduce the service life of synchronous condenser.In order to research the above problems,the end magnetic field,loss,electromagnetic force and building bar’s partial discharge of 300 MVar synchronous condenser under no-load,over excitation and under excitation conditions are studied in this paper.The research results provide theoretical basis for finite element calculation of transient field and improvement of end magnetic field distribution of the synchronous condenser.The main research results are as follows:(1)The simulation model of the three-dimensional transient electromagnetic field at the end of the synchronous condenser is established considering the nonlinear factors such as magnetic saturation and distortion,and the accuracy of the model is ensured by experiments;(2)The variation of magnetic density and loss of end structures with operating conditions is revealed,and the influence of different metal shield materials on the magnetic density and loss density is obtained;(3)By studying the electromagnetic force at the end of stator winding in steady state and transient state,the variation law of electromagnetic force density at the end of stator winding in steady state is revealed,and the position of stator end winding with the largest fluctuation of electromagnetic force density is obtained;(4)The distribution of magnetic flux density and the induced electromotive force of the building bar under different operating conditions are compared.The factors affecting the partial discharge of the building bar and the core are revealed,and the partial discharge risk assessment of the building bar is obtained.