Research On Single-phase Grounding Fault Location Method Of Generator Stator

Single-phase grounding of the stator is the most common type of fault in generators.When the stator single-phase grounding fault of the generator occurs,if the fault is not checked in time,the fault current will endanger the stator core and even develop a more harmful phase-to-phase and inter-turn short circuit fault.Therefore,the design of the protection scheme for the stator single-phase grounding fault of the generator becomes especially critical.The timely detection of the stator grounding fault can greatly reduce the probability of the generator internal short circuit fault.If the specific fault location can be continuously detected,it will greatly help the subsequent processing of the generator stator winding grounding fault.In this paper,the single-phase grounding fault location method of generator stator is studied.In this paper,the following main contents are used to study the single-phase grounding fault location method of generator stator:Firstly,the electric potential characteristics such as winding potential,zero-sequence voltage and three-camera voltage after generator single-phase grounding fault are analyzed,which provides a theoretical basis for the positioning method;a method for measuring fault parameters of generators is proposed.By injecting current signals from the delta side of the open side of the voltage transformer,the return voltage of the open side of the voltage transformer and the induced voltage of the low-voltage star side are measured respectively,based on the injected signal and measured.The return signal can accurately calculate the ground capacitance and fault resistance value after the single-phase grounding fault of the generator stator;based on the equivalent zero-sequence network after the generator stator grounding fault,combined with the measured ground capacitance and the fault resistance parameter after the generator stator grounding fault,accurate analysis of the phase angle between the fault winding potential and the phase potential,so as to achieve accurate positioning of the generator stator grounding fault.The fault parameter measurement method proposed in this paper is mainly operated on the low voltage side of the voltage transformer.The measurement process is safe and the wiring is simple.The measurement method avoids the influence of the short circuit impedance of the voltage transformer,and the result is accurate.The principle of the fault location method is simple and easy to overcome.The original positioning method causes a large error when the calculation accuracy of the transition resistance is insufficient,and the accuracy of the positioning result is effectively improved.The simulation results show that the proposed parameter measurement method selects the optimal injection frequency combination through different injection signal frequencies,and can accurately measure the ground capacitance and fault resistance parameters after the generator fault.The proposed fault location method can accurately locate the fault point under various conditions of different neutral point grounding modes of the generator through different transition resistances and different position faults,and provide assistance for the subsequent processing of the fault.