Frequency and time fault diagnosis methods of power transformers

Abstract

The authors describe experimental and theoretical analyses of faults of power transformer winding. Faults were caused by mechanical effect of short-circuit currents. Measurements of transformer were carried out in high-voltage laboratory. Frequency and time diagnostic methods (method SFRA - Sweep Frequency Response Analysis, impact test) were used for the analyses. Coils of transformer windings were diagnosed by means of the SFRA method and the time impact test. The analyzed methods had a significant sensitivity to a relatively small deformation of coil. In the analysis a new technique for analyzing the effects of short-circuit currents is introduced. This technique is developed for high-voltage transformers (different types of power). The proposed analyses show that it is necessary to analyze the value of short-circuit current. Short-circuit current represents a danger for the operation of the power transformer. The proposed approach can be used for other types of transformers. Moreover, the presented techniques have a potential application for fault diagnosis of electrical equipment such as: transformers and electrical machines.

Fault diagnostics of transformer winding in time and frequency domain

“…This method enables detecting early states of the winding faults. Short-time voltage pulses are applied to the winding in order to create a voltage gradient across the complete coil of the winding [10].…”

Diagnostics of Transient States in Hydraulic Pump System with Short Time Fourier Transform

“…In our study we would like to point out, that STFT can be applied in diagnostics of dynamic changes in the test rig. Obtained spectrograms are used to estimate the frequency content of signals especially with low amplitude changing over time and this is an advantage over standard FFT method [7].…”

Identification of Power Transformer Winding Fault Types by a Hierarchical Dimension Reduction Classifier

“…According to a statement in [8], statistics show that 70% to 80% of failure regarding power transformers are caused by undetected winding faults. Commonly used approaches for detecting incipient winding faults are usually offline tests, such as the short-circuit impedance measurement (SCI) [9], low-voltage impulse tests (LVI) [10], and frequency response analysis (FRA) [11][12][13][14][15].…”

“…Among the existing test approaches, FRA is a well-recognized technique for diagnosing incipient winding faults in power transformers [11][12][13][14][15]. Depending on the types of injected signals, there are two major types of FRA, which are the sweep frequency response analysis (SFRA) and impulse frequency response analysis (IFRA) [8].…”

“…Then, the frequency response (FR) is derived by converting the results to a frequency domain [16]. Based on the comparing the studies in [8,15], the results and sensitivities of SFRA and IFRA are similar for detecting faults in the short circuit. However, in some literature [17], it states that IFRA could encounter drawbacks of low resolution in low frequencies.…”