Potential transformer is the basic equipment for voltage monitoring and protection of power system. The voltage transformer and its secondary circuit will

once in case of defect

likely cause abnormal alarm of voltage circuit and abnormal protection action of relaying protection as well as threaten the normal operation of the power grid. This paper starts from the defect of voltage alarm in the operation of a busbar voltage transformer in a power plant

the site inspection and defect analysis are described in detail. The method of internal circuit simulation model of the defect of the voltage transformer is set up to simulate the actual abnormal process

the simulated transient waveform with the same characteristic quantity as that of actual transient characteristic quality is obtained by calculation

thus the theoretical analysis conclusion is verified. Finally

the other types of common defects of typical instrument transformer

which are replicated by using the method in the work is briefly listed. The secondary voltage characteristic of the instrument transformer corresponding to different defects is compared and analyzed. Moreover

the feasibility and application prospect to achieve the defect monitoring and identification based on the waveform characteristic quality is described.