Investigating the Capacitive Inter-Winding Response of Power Transformer

Theoretical considerations while applying sweep frequency response analysis method in determining the interwinding capacitance of power transformers at higher frequencies

“…Pertinent literatures relevant to the present study are grouped into three categories and are discussed as follows. Correlating interwinding capacitance to the diagnostic status of a transformer The circuit constant values of the interwinding capacitance of transformer winding insulation are jointly governed by the design criteria, geometry, structural factors, and the materials used, respectively . Henceforth, it is easy to assume that the interwinding capacitance carries not only information regarding the winding‐core arrangement but also reveals the status of the winding insulation, respectively.…”

“…Such deformations appear predominantly at the interwinding capacitances as the susceptance measured is expected to be purely capacitive in nature. Nevertheless, the current capacitive susceptance measured using the method as proposed in the literatures, IEEE and IEC standards are not purely capacitive, instead suffer a slight influence of winding‐core assembly . This influence causes a small kink appearing in the mid‐frequency region.…”

“…Analyzing interwinding capacitance of transformers is one of the apparent methods used for assessing the integrity of winding‐core and winding‐insulation arrangements . Naturally, sweep frequency response analysis (SFRA) method and frequency domain spectroscopy (FDS) are increasingly used .…”

“…Understanding its importance, the current IEEE and IEC standards have included an interwinding capacitance measurement expecting to widen the possibilities of SFRA method in determining insulation status of the transformers . Nevertheless, the proposed methods are inadequate in revealing the actual interwinding capacitance of transformer . Considering this, a thorough investigation on theoretical considerations is required, whereas expanding the potential of SFRA method in measuring the interwinding capacitance is investigated.…”

“…Later, depending on the information obtained, the requirement of a detailed FDS analysis could be decided. In all, the deviation in the condition of winding insulation appears more prominent at the interwinding capacitance or in the capacitive susceptance function . Hence, a simple comparative analysis would be enough to ensure the diagnostic status of the winding‐insulation arrangement.…”