Translated Abstract
Cross-linked polyethylene cables with small dielectric loss, higher operation temperature, convenience for cabling and simpler maintenance are widely used. Particularly in HV and Ultra HV area, the XLPE cables have become first choice of power cables for hydf the cable performance on the basis of systemic test, the 500kV XLPE power cable is designed and developed in this paper. It is shown by test results that the design reaches to the predefined goal and the cable can be produced in batch. The current capacity, short time over current capacity and short circuit current of XLPE cable with conductor cross-section of 1�mm2 are calculated by IEC287 standard and concentrated parameter method respectively in this paper. The calculation results show this is a feasible and accurate method. Therefore, the conductor cross-section of 500kV cable designed by above-mentioned methods completely satisfies with the requirement of practicable engineering. A proper cross-section of conductor with 800mm2 is found by the current capacity of 500kV XLPE cable. There are two methods to design the insulation thickness of XLPE cable such as maximum stress and average stress. According to the suffered voltage of 500kV XLPE cable in operation and the insulation level, tow design principles of maximum and average stresses are analyzed and compared by design experience abroad through the theoretical analysis of relationship of field distribution, homogeneity and breakdown strength of insulation with the insulation thickness. Finally the average stress method is used due to it can reflect the influence of electrical and thermal field on the properties of insulation. The insulation thickness of 32mm2 for 500kV XLPE cable is finally fixed by the design and calculation of insulation under power frequency and impulse voltage. Alloy lead, aluminum, stainless steel are the materials of metal sheath in cable. The Al sheath structure is selected by comparison of different metals and combination of customer’s requirement for practical use. The short circuit capacity of the Al sheath calculated by process of IEC949 standard for non thermal isolation state is proved by test. The results show that the short circuit capacity of the sheath in XLPE cable by this method reaches to practical design. Finally, the reference standard, requirement, method and results of type approval test for 500kV XLPE cable are introduced and discussed. The reliability of cable designed and developed in this paper is proved by the test.
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