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The different phase resolved partial discharge patterns, which can be recognized when a positive dc voltage containing a ripple due to a half-wave rectification is used are presented in this paper. Results are given from corona onset to the appearance of breakdown streamers. The outcomes are five different patterns, which represent the four stages of positive corona and their transition zones. Three of them are clearly identifiable with respect to patterns from other discharge sources that have already been reported for dc voltages containing a ripple. For an assessment of pattern formation discharge pulses as recorded at the test object are presented. Finally, the appearance of patterns is explained with support of the measured discharge pulses and the underlying physical processes.

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In this paper a new two stage equivalent circuit for corona discharges is introduced. Its aim is to fill the gap between complexity of the circuit and accurate representation of the physical properties, which underlay a corona discharge. The first stage represents the voltage distribution and the occurrence of a discharge with respect to the applied voltage. The second stage models the physical discharge behavior like ionization, number of electrons, positive and negative ions as well as their interaction. The proposed circuit is able to model the different modes of corona discharges, which is experimentally verified. The simulation results are in good agreement with the measured results but cannot compete with simulations based on solving continuity equations. Nevertheless, due to the solely basement on network theory, it provides an easy access to the occurring physical effects during a corona discharge for all electrical engineers.