Investigations on surface discharge at a cable termination arrangement under medium voltage AC and Damped AC (DAC)

Inhalt:
The measurement and diagnosis of high-voltage (MV and HV) cables as part of commissioning tests On-Site place particular challenges on the selected testing system due to high capacitive properties of the cables system. To circumvent the problems of high reactive power demand during a test, resonant testing systems are widely used to perform an AC testing closely to the operational voltage. Despite the advantage of reducing the effort regarding the reactive power demand, resonant testing systems still represent an immense mechanical effort. As an alternative for resonance testing, the Damped AC method can be used. This paper presents the results of previous investigations regarding the ability of Damped AC test voltage and 50-Hz-AC to detect service-endangering failures in manner of a reproducible needle defect. Despite the heaviest possible damaging inside a cable insulation, the needle defect, most real cable failures can be attributed to introduced errors during the assembly of cable accessories. These failures lead in most cases to surface discharge inside the accessories at the stripped conductive layer edge of a cable geometry. To further investigate the performance of the DAC1 test method to detect service endangering accessory defects, surface discharge investigations are presented in order to create an artificial reproducible surface discharge error on full scale cable specimen.