Challenges on the measuring and testing techniques for UHV AC and DC equipment

摘要

After an introduction of the actual IEC Publication concerning high voltage test andmeasuring techniques with the relation between the lightning and switching impulse voltageto the highest voltage for equipment (AC or DC) the generation and measurement of thedifferent types of test voltages are described.The required AC test voltages in the range of 1200 to 1800 kV could be generated bytransformer cascades or by resonance test systems, where the resonance conditions could bereached by variable inductance for a fixed frequency or by variable frequency for a fixedinductance. AC measurements are combined with partial discharge and dielectricmeasurements and therefore suitable coupling and standard capacitors are required.Switching impulse voltages in the range of 1800 to 2400 kV and lightning impulses in therange of 2800 – 3500 are generated with Marx generators. Due to the large test circuits forUHV apparatus and the limited space in the test field the electrical field stress should becontrolled by proper design of the electrodes; concerning the impulse shape oscillations areexpected and should be handled. The main parameter for impulse voltage measurements arethe influence of the proximity effect, the linearity of the voltage divider ratio and the newproposal for the evaluation of impulse voltage with superimposed oscillations near the peak.The required DC voltages in the range of 1500 to 2000 kV are generated by rectification of ahigh AC voltage and multiplying the output DC voltage of a single stage by a cascadearrangement. The DC measurement is done by a resistive voltage divider with a capacitivegrading to prevent damages in case of a test object flashover or breakdown.Test voltage generators and measuring systems for UHV apparatus are available or could bemanufactured and here the experience from the seventies and eighties could be used.