XLPE电缆在电热老化过程中交流空间电荷特性的试验研究

Crosslinked Polyethylene（XLPE）cable has been widely used in power system. It is an important part in XLPE cable insulation condition monitoring how to estimate and forecast the insulation degradation degree of XLPE cables in operation，while no relevant research has been reported so far in our country. The probable imperfect manufacturing process, impact from work voltage and overvoltage during operation, temperature variation caused by current deviation or voltage-multiplying during withstand voltage test may weaken the cable insulation,especially space charge effects alter the local electric field,influence the insulation properties and contribute to electrical tree initiation,therefore space charge characteristics in cables are worthy of concern.This project aims to measure and research space charge characteristics of XLPE cable under AC electrical-thermal aging, make research on the effects of space charge's accumulation, distribution and transportation on cable insulation aging characteristics in the electrical-thermal aging process and after repetitive withstand voltage tests, analyze the relevance between AC and DC space charge characteristics and aging degree of cable. This study is of much importance for estimating the insulation degradation degree of XLPE cables, judging damage situation of cables after withstand voltage tests, enriching the theory of diagnosis and estimation for cable insulation, avoiding burst faults of cables and ensuring stable operation of power system.

XLPE电缆目前广泛地应用于电力系统中，如何评估和预测现场运行电缆的老化及早期劣化的程度是电缆绝缘状态评估的重要内容，然而这项研究在国内仍是空白。鉴于XLPE电缆制造工艺的过失、运行中承受的工作电压和过电压的冲击、载流量变化引起的温度变化以及耐压试验受到的倍压都可能造成XLPE电缆绝缘特性的改变，特别是空间电荷的积累与作用对电缆绝缘的影响是不可忽略的。本申请拟针对工程用XLPE电缆本体展开交流电压作用下电热老化过程中空间电荷特性的测试与研究，研究工程用XLPE电缆本体在加速电热老化过程中和反复耐压试验时，其交流空间电荷的积累、分布和迁移特性对电缆绝缘老化特性的影响，以及电缆老化后交直流空间电荷的特性与电缆老化程度的关联特性，这对于评估XLPE电缆绝缘的劣化程度以及耐压试验对电缆绝缘的破坏情况，完善电缆绝缘故障诊断与状态评估理论、防止电力电缆突发性故障，保障电力系统正常运行有十分重要的意义。

本项目对工程用XLPE电缆本体展开了交流电压作用下电热老化过程中空间电荷特性的测试与研究，研究工程用XLPE电缆本体在加速电热老化过程中和反复耐压试验时，其交流下空间电荷的积累、分布和迁移特性对电缆绝缘老化特性的影响，以及电缆老化后交流下空间电荷的特性与电缆老化程度的关联特性，为预测XLPE电缆绝缘的劣化程度、完善电缆绝缘故障诊断与状态评估理论提供理论和实践依据。结题报告总结了本项目的研究工作，本项目研制搭建了电缆本体空间电荷测量系统与电热老化平台，并对10kv电缆进行了恒温老化箱老化与温度梯度场老化两种老化方式的电热加速老化。研究了不同老化方式下交流电压下电缆本体空间电荷的积累、分布及迁移等特性。同时还研究了不同老化方式下电缆绝缘老化的空间电荷特性与相关特性（机械特性、电气特性、理化特性）的变化。较好地完成了本项目的各项任务，达到了预设目标。