Construction and Application of Online Vibration Frequency Response Analysis Method for Converter Transformer Winding

ABSTRACT The harmonic current and vibration of a converter transformer are effective pieces of information for detecting mechanical faults in the winding. In this paper, the ratio of vibration acceleration to the current squared is defined as the vibration frequency response function (VFRF) of the winding, and then, a novel online vibration frequency response analysis (VFRA) method is constructed. A harmonic load platform is built to simulate the real operating environment of the converter transformer, and it is verified by experimental methods that online VFRA is a simpler and more convenient method for winding mechanical condition detection than offline VFRA. The effects of different factors such as current magnitude and harmonic content on the online VFRA are investigated, and the converter transformer winding mechanical condition is detected by combining the VFRF trace with two numerical indices of Lin's concordance coefficient (LCC) and improved comparative standard deviation (CSD). Laboratory experiments demonstrate that online VFRA has high stability and can effectively diagnose winding looseness faults of different degrees. In contrast to the traditional frequency response analysis (FRA) and short‐circuit impedance (SCI) methods, online VFRA has higher sensitivity and detection capability, and is a better method for online monitoring of the winding mechanical condition.