Due to their excellent electrical insulation properties and processability, polymer materials are used in many electrical products. It is widely believed that space charge plays an important role for the electric field distribution, conduction, ageing, and electric breakdown of polymeric insulation. This paper reviews measurements and characteristics of space charge behavior which mainly determined by the pulsed electro-acoustic (PEA) measurement technique. Particular interests are the effects of the applied voltage, the electrodes, temperature, humidity, microstructure, additives, and filler materials on accumulation, distribution, transport, and the decay of space charge in polymeric materials. This review paper is to provide an overview on various space charge effects under different conditions, and also to summarize the information for polymeric materials with suppressed space charge and improved electrical behavior.
Hydrophobic cycloaliphatic epoxy (HCEP) has been used as outdoor insulation material to maintain good electrical performances under multiple stresses, in which acidic attack to this kind of materials has been causing concern in recent years. To study the performances of HCEPs under acid rain, a new acid fog test method has been established and an acid fog chamber was constructed. During the 1000 h acidic rain test, contact angles of the HCEPs decreased and the less hydrophobic samples had higher leakage currents. Increase of the surface roughness and diameters of the micro holes have been observed by AFM and SEM, and oxidation of surface groups was analyzed by FTIR. Resistance to tracking and erosion remained good after the 1000 h test. The results showed that HCEPs exhibited good outdoor insulation performances in acidic fog under DC stress.
We apologize for the following misprints in the review paper with title \Research progress on space charge characteristics in polymeric insulation", published in Vol 6./No. 1 of the \Journal of Advanced Dielectrics". (1) In the citation of Fig. 6, Ref. 5 should be replaced by Ref. 32. (2) In Fig. 10, Ref. 119 should be replaced by Ref. 120. (3) In Table 1, Ref. 20 should be replaced by data partially from Ref. 35. (4) On Page 5, left column, first paragraph of Part 3.3, last sentence \See Fig. 6 as an example for change density …" \change" should be \charge".
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