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Title: Simultaneous space charge and current measurements in polyethylene insulation under HVDC conditions
Author: Lau, Wai Shyan
ISNI:       0000 0001 3605 5503
Awarding Body: University of Southampton
Current Institution: University of Southampton
Date of Award: 2003
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This thesis reports on the construction of an improved Pulsed Electro-acoustic (PEA) fully automated measurement system. This system is capable of not only measuring space charge but also current simultaneously on thin plaque specimens under a controlled temperature environment. This additional valuable piece of information enhances comprehension on their relationship. They complement each other to give details about charge carrier generation, transportation and accumulation processes.  Additive-free low density polyethylene (LDPE) is the basic element of crosslinked polyethylene (XLPE); it was chosen for initial testing to eliminate the contribution of the impurities (by-products created in XLPE due to the usage of crosslinking agent).  Electrode materials and measurement temperature had been confirmed to affect space charge and current performance intensely. Measurements were also carried out on XLPE (degassed and undegassed) at different temperatures to study the differences as compared to LDPE. It is believed that the by-products (acetophenone, α-methylstyrene, cumyl-alcohol etc.) in undegassed XLPE have played an important role in creating consecutive fast moving charge packet activity (using solid aluminium cathode and semicon anode) where this happened neither in degassed XLPE nor LDPE. Further tests were carried out using LDPE soaked in chemicals, namely acetophenone, α-methylstyrene and cumyl-alcohol that are found in undegassed XLPE to examine the contribution of each chemical on charge and current responses. All these by-products had proven to increase the conductivity of the charge carriers. Their presence have enhanced either one or both signs of charge carriers being injected from the electrodes.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available