Testing and analysis of universal high voltage divider

Abstract

A newly built universal high voltage divider designed by VTT MIKES technical research center of Finland is developed to measure DC, AC, SI, LI, composite and combined waveforms. In comparison with a RC divider, the RCR divider is also utilized to measure DC voltages. All different kinds of waveshapes can be measured within prespecified voltage level limits and therefore the name “universal” divider is given to the RCR divider. Preliminary calibration tests have been done by VTT to verify the short-term performance of this device. The assembly, dynamic behaviour analysis, PD measurements and different types of voltage stressing of this non-commercial RCR divider are done at the high voltage laboratory of Tampere University and are in general the main content of this thesis. The ultimate goal is that the device can be used by national metrology institutes to calibrate commercial universal HV dividers and therefore the device can be called a reference HV divider. Due to the large amount of different measurements executed in TAU's HV lab, only a few types of measurements are explained and discussed in detail in this final work. The conclusion at the end is based on all the measurements that are carried out at the HV lab. The thesis aims in general to give a profoundly and well-illustrated explanation of the executed measurements and their results. The unit step response and partial discharge measurements are done in accordance with the IEC standards. This implies that the test results are valuable and thus can be used for further test measurements or for comparison with other high voltage dividers. References to these standards and interpretation of the norm will be done were needed to increase the fidelity of the thesis. High voltage dividers are one of the components of a high voltage measurement system. The task of these HV dividers is to reduce the high voltage to voltage levels that are appropriate for our measurement devices (low voltage) without causing any distortions on the waveshape. The decrease in voltage level is described by a dividing ratio also known as the scale factor SF of the HV divider. Mankind has developed a broad range of high voltage dividers. The most common classification is based on the kind of wave shapes and directly correlated with it, are the voltage levels that these high voltage dividers are able to measure. There is noticeable evolution in the development of high voltage dividers where designers try and succeed to improve these measurement devices. The literature study includes an overview of the different kinds of HV dividers and explains the main differences between them according to the working principle, circuit and specifications. The main problems that these high voltage dividers are facing will be discussed to indicate the flaws of these devices. This background is needed to gain insight and to understand the main part of the thesis better, the testing and evaluation of the RCR high voltage divider itself. At the end a summary of the main outcomes of this thesis will be presented to the reader and further possible research will be indicated.