Transformer Oil Viscosity Measurements Using a Love Wave Sensor

In this paper, a Love wave (LW) sensor is investigated as a possible device for the estimation of the quality of transformer oils. The magnitude response and the phase of the transmission coefficient (S
21
) of the LW sensor was measured with a Vector Network Analyzer. It was shown that the viscosity of the transformer oil which is an indicator of its quality led to a reduction in the magnitude of the S
21
coefficient and a frequency shift. A relationship between frequency change and viscosity was identified, with higher viscosity leading to greater frequency change. Comparatively to the literature, the attenuation of the transmission coefficient is in agreement with a linear variation expected to the parameter (viscosity*density)
^0.5
. The study also identified the behavior of S
21
when observed in the time domain. The results let us conclude that LW sensors can be used as a candidate for the real time monitoring of transformers oil quality.