Abstract
This paper aims at investigating the electrical tree characteristics of isotactic polypropylene (iPP)/syndiotactic polypropylene (sPP) blends for thermoplastic cable insulation. PP blended samples with sPP contents of 0, 5, 15, 30, and 45 wt% are prepared, and electrical treeing experiments are implemented under alternating current (AC) voltage at 50, 70, and 90 °C. Experimental results show that with the incorporation of sPP increasing to 15 wt%, the inception time of electrical tree increases by 8.2%. The addition of sPP by 15% distinguishes an excellent performance in inhibiting electrical treeing, which benefits from the ability to promote the fractal dimension and lateral growth of branches. Further increase in sPP loading has a negative effect on the electrical treeing resistance of blended insulation. It is proved by DSC and POM that the addition of sPP promotes the heterogeneous crystallization the of PP matrix, resulting in an increasing density of interfacial regions between crystalline regions, which contains charge carrier traps. Charges injected from an electrode into a polymer are captured by deep traps at the interfacial regions, thus inhibiting the propagation of electrical tree. It is concluded that the modification of crystalline morphology by 15 wt% sPP addition has a great advantage in electrical treeing resistance for PP-based cable insulation.
Highlights
As a promising type of environmentally friendly and recyclable insulation, polypropylene (PP)has attracted wide attention for its advantages of excellent electrical and heat resistance properties [1,2].Nowadays, PP-based insulation cable has been in use by thousands of kilometers in medium voltage power systems in Europe
The crystal morphology and the trap energy level characteristics of blended samples are analyzed, and a discussion based on the electric field affected by the aggregation structure has been provided to help in understanding the mechanism of microscopic crystallization on macro degradation
With the incorporation of sPP increasing to 15 wt%, the inception time of electrical tree increases by 8.2%
Summary
As a promising type of environmentally friendly and recyclable insulation, polypropylene (PP)has attracted wide attention for its advantages of excellent electrical and heat resistance properties [1,2].Nowadays, PP-based insulation cable has been in use by thousands of kilometers in medium voltage power systems in Europe. As a promising type of environmentally friendly and recyclable insulation, polypropylene (PP). Has attracted wide attention for its advantages of excellent electrical and heat resistance properties [1,2]. PP-based insulation cable has been in use by thousands of kilometers in medium voltage power systems in Europe. And Netherlands are the first countries to promote modified PP material in cable insulation. Spain and Finland have successively promoted modified PP as cable insulation material in medium voltage power systems [2,3]. Under the continuous action of the electric field, the insulation will gradually deteriorate and may induce breakdown, which may threaten the normal operation of the power system. Inhibiting the initiation and growth of electrical tree in polypropylene insulation is the basis of accelerating the practical application of polypropylene insulation [4]
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