Development of measuring techniques for high voltage impulse and small signals using Pockels cell

A recent increase in electric power demand requires stable power supply, which could be achieved by improving the diagnostic and preventive methods for the power apparatus. For this purpose, it is highly necessary to develop better measuring techniques for not only the fast transient impulse voltages but small signals. The former, coming into the substation, are produced by the overvoltages taking place in the power energy system. Regarding the latter, their patterns should be recognized since the pulse-type small signals could indicate actual insulation condition of electric power apparatus in which partial discharges are generated. In this work, optical measuring system was constructed to measure high voltage impulse and pulse type small signals by use of the KDP and lithium niobate Pockels cell respectively. Transverse mode was adopted for the application of the voltage to be measured, since it is possible to obtain different half wave voltage by controlling the minute dimensional variation of the crystal in use. The characterization of the constructed system was also performed.