Space charge and charge trapping characteristics of cross-linked polyethylene subjected to ac electric stresses

2016 IEEE Electrical Insulation Conference (EIC)

Vaughan

et al. 2016

-Polyethylene exhibits many key characteristics including low dielectric loss, high breakdown strength and good processability. Most modern extruded high voltage cables employ cross-linked polyethylene (XLPE) as the insulation material. The main advantage of XLPE is its excellent thermo-mechanical properties; it is relatively cheap and has low dielectric loss and low conductivity making it an ideal material for this application. Crosslinking enhances a number of thermo-mechanical properties such as deformation resistance at higher temperatures, tensile strength and creep properties. In comparison with low density polyethylene (LDPE), the heat deformation characteristics of XLPE are superior and, for this reason, XLPE is currently the most common insulation material for power cables ranging from low to high voltages. This paper reports on an investigation into the development of a new XLPE formulation for use in high voltage direct current (HVDC) cable applications. Specifically, the electrical performance of two novel LDPE resins are compared with an industrial standard (reference) LDPE material. For crosslinking, dicumyl peroxide (DCP) was selected, as the decomposition temperature is high enough to prevent pre-curing during processing and to allow an efficient and rapid crosslinking at moderate temperatures. Moreover, the behavior of various systems is compared in terms of electrical breakdown performance and the influence of material composition and processing on these parameters is described.

Section: Degassingmentioning

confidence: 99%

The effect of composition and processing on electric characteristics of XLPE in HVDC cable applications

2016 IEEE Electrical Insulation Conference (EIC)

Vaughan

et al. 2016

“…It is well known that crosslinking agents produces byproducts within the material as a result of the crosslinking reactions [8,9]. Therefore, all samples were degassed in a vacuum oven for 6 d at a constant temperature of 70 ℃ to remove volatile residual byproducts from the crosslinked samples.…”

Section: Degassingmentioning

confidence: 99%

“…For space charge characteristics, the PEA method is the most widely used for HVDC cables. This technique utilizes the interaction between high voltage pulses and charge layers accumulated in the insulating material to produce acoustic pressure waves, which transverse across the material [8].…”

Section: Introductionmentioning

confidence: 99%

The effect of electrode material and semicon bonding on space charge dynamics of XLPE

2016 IEEE International Conference on Dielectrics (ICD)

Vaughan

et al. 2016

-This study sets out to explore the space charge characteristics of high voltage direct current (HVDC) cable grade crosslinked polyethylene (XLPE) using different electrode materials and configurations, ranging from sputtered gold to thermally bonded semi-conducting materials. The existence of both homo and hetero charges in HVDC cables is well known; however, the role of semi-conducting materials and the formation of space charge is critical and required more attention. Space charge accumulation at high electric stress was monitored using the pulsed electroacoustic (PEA) technique. Experimental results have shown that charge injection processes take place in all cases and the amount of charge and polarity of the dominated injected charge has significant dependence on the electrode material under the same applied electric field.

“…In common with other crosslinking agents, DCP also produces byproducts (curing decomposition product) within the material from the crosslinking reactions and this can influence electrical and thermal properties of the material [14,15]. The most common approach to remove the byproducts adopted by the cable manufacturer is degassing.…”

Section: Degassingmentioning

confidence: 99%

The impacts of the temperature and electric field on the electrical characteristics in semicon-bonded XLPE insulation

2016 IEEE International Conference on High Voltage Engineering and Application (ICHVE)

Chen

et al. 2016

-HVDC cables play a vital role in the power transmission system for renewable energy and global power trade. Nowadays, the crosslinked polyethylene (XLPE) extruded cables have been widely applied in power industry due to the superior performance on the thermo-mechanical properties and dielectric properties. The low volume conductivity and the minimized space charge accumulation are the two key requirements for a reliable high voltage direct current (HVDC) cable insulation. This paper reports on the impact of temperature and electric field on the space charge behavior and DC conductivity in XLPE material for cable insulation. The samples were carefully prepared to simulate the real cable insulation structure. A layer of LDPE film mixed with DCP (dicumyl peroxide) was sandwiched between two layers of semicons (also contain crosslink agent) and then crosslinked at 200 ᵒC to ensure the semicon layers were thermally bonded with the XLPE insulation. The crosslinked samples were then degassed in the vacuum oven with for 6 days at 80 ᵒC. The space charge characteristics and the conductivity of the semicon-bonded XLPE samples were measured at room temperature and high temperature. The electric fields were kept at 20 kV/mm and 40 kV/mm and the influences of the electric field and the temperature on space charge dynamics and conductivity in the semicon-bonded XLPE samples are discussed.