Dielectric Spectroscopy in High Voltage Machines Diagnostics

The HV machines windings and insulation are constantly exposed to a combination of heat, electric and mechanical stresses. All of these factors have influence on the state of the machines winding insulation. The state of winding insulation is one of the studied parameter that can detect an upcoming failure. There are few measurements methods used to winding insulation state assessment as electric resistance measurement using DC current, partial discharge measurement, dielectric response measurement, capacitance and dissipation factor measurement measured at power grid frequencies and dielectric spectroscopy.

The FDS is a method that utilized an AC current excitation of studied material (transformer insulation). The capacitance and the dissipation factor are measured as a function of frequency of the excitation signal. A base block diagram of an FDS analyzer with a typical connection to a device under test (DUT) is shown in Fig. 1. A typical dissipation factor course measured using the FDS method is shown in Fig. 2.

Fig. 1 The block diagram of the dual channel FDS analyzer — Fig. 1 The block diagram of a dual channel FDS analyzer

Fig. 2 The typical FDS measurement result and factors affecting the dissipation factor

My main goal is to design a hardware platform providing an analog to ditigal interface suitable for the FDS method. The platform should improve measurment parameters of the commonly market available FDS analyzers. A board equipped with an analog to digital (ADC) and a digital to analog (DAC) converters was designed. A block diagram of the board is shown in Fig. 3 and a 3D model of the designed front-end is shown in Fig. 4.

Fig. 3 The block diagram of the designed analog front-end board

Fig. 4 The 3D model of the designed front-end — Fig 4. The 3D model of the designed front-end

Related publications:

O. Teren, J. Tomlain, R. Sedlacek and J. Vedral, "The design of an analog to digital front-end for frequency domain spectroscopy analyzer," 2016 15th Biennial Baltic Electronics Conference (BEC), Tallinn, 2016, pp. 155-158.

Tereň, O.; Tomlain, J., "An analog to digital front-end for frequency domain spectroscopy analyze", In: Proceedings of the 20th International Scientific Student Conferenece POSTER 2016. Praha: Czech Technical University in Prague, 2016. ISBN 978-80-01-05950-0.