Space charge dynamics in pressboard-oilpressboard multilayer system under DC voltages

Converter transformers play a critical role in HVDC power transmission system. Space charge is a general concern for dielectric system under DC field. In this paper, the space charge behavior in a sandwiched oil-pressboard insulation system has been investigated using the pulsed electro-acoustic (PEA) method. The presence of homo-charges in the pressboards bulk and hetero-charges at the two interfaces between oil gap and pressboards leads to the electric field enhancement in the pressboards but reduction in the oil gap. The electric field enhancement is much larger than the value estimated by the Maxwell-Wagner polarization.