Research on On-Line Detection Method of Transformer Winding Deformation Based on VFTO

Area of Science:

• Electrical Engineering
• Power Systems Analysis
• Diagnostic Techniques

Background:

• Transformer winding deformation faults are currently detected offline, requiring planned outages or post-failure analysis.
• Real-time online monitoring of winding status during operation is challenging.
• Very fast transient overvoltages (VFTO) occur during transformer operation and can be utilized for diagnostics.

Purpose of the Study:

• To propose and validate an online method for detecting transformer winding deformation faults using VFTO.
• To investigate the frequency response characteristics of transformer windings under VFTO impact.
• To establish a correlation between frequency response changes and winding deformation parameters.

Main Methods:

• Simulated VFTO generation and injection into an equivalent transformer winding circuit model.
• Establishment of circuit models for both undeformed and deformed windings.
• Analysis of resonant frequency shifts in the frequency response curves under varying deformation types and degrees.
• Experimental validation using simulated winding faults.

Main Results:

• Distinct frequency response curve changes were observed for different winding deformation types.
• Simulated increases in radial capacitance, series inductance, and longitudinal capacitance led to measurable shifts in resonant frequencies.
• The degree of simulated fault inductance change directly correlated with a shift in the frequency response curve towards lower frequencies.
• Experimental results confirmed the feasibility of the online detection method.

Conclusions:

• The frequency response method, when combined with VFTO analysis, offers a feasible approach for online detection of transformer winding deformation.
• Changes in resonant frequencies comprehensively reflect the type and degree of winding deformation.
• This online method can potentially reduce the need for offline diagnostics and improve transformer operational safety.