现役交流XLPE电缆绝缘切片试样的交、直流耐压性能对比  

Comparison of AC and DC Voltage Endurance Properties of Insulation Sheet Samples Spirally-cut from Existing AC XLPE Cables

作　　者：刘英[1] 姜晖 曹晓珑[1] 

机构地区：[1]西安交通大学电力设备电气绝缘国家重点实验室,西安710049

出　　处：《高电压技术》2017年第11期3559-3567,共9页High Voltage Engineering

基　　金：国家自然科学基金(51777156);国家重点研发计划(2016YFB0900703);国家电网公司科技项目(SGZJZSOOHYJS1700217)~~

摘　　要：为升级输电线路的传输能力,可将现役交流XLPE电缆线路改为直流运行,但仍缺乏改造方案设计的统一标准或规范。因而对1根投运7年的YJV22-8.7/10 kV-3×185 mm^2电缆进行绝缘环切,在相同条件下对切片试样进行交流及直流电压下的连续和逐级升压击穿试验。结果表明:升压速率为2、0.5、0.1 kV/s的连续升压击穿试验中,升压速率对试样的交流平均击穿场强影响很小,而对直流击穿场强影响较大;时间步长为2、6、15 min的逐级升压试验中,随着时间步长的增加,交流击穿场强略有降低,而直流击穿场强显著增大。随着电压施加时间的增加,交流击穿场强下降,而直流击穿场强反而增大,这导致直/交流击穿场强比值持续增大,由1.33增大至3.73。以击穿场强的95%置信下限值为基础,推导可获得XLPE绝缘试样的交、直流1 h击穿场强分别为89.50 kV/mm及247.55 kV/mm,而反幂定律中的电老化寿命指数拟和值为17和-11.51。在高压短时击穿试验范围内,试样的直流耐压性能随时间变化不符合传统电老化寿命定律,这可能与空间电荷效应的时间依赖性有关,需要后续研究进一步确认;同时也说明基于薄试样、高电压、短时间的击穿试验数据无法有效反映直流绝缘的长期电老化性能,不能直接用于XLPE直流电缆的绝缘结构设计。It is a feasible way to transform an existing XLPE cable line from AC operation into DC operation for uprating the transmission capacity, but there is no unified standard or specification for the transformation design till now. We pre- pared sheet samples by spirally cutting the XLPE insulation of a YJV22-8.7/10 kV-3 185 mm2 cable which had been running for 7 years, and the breakdown tests were performed under continuous-rising and step-up voltages, both AC and DC, with the same conditions. The results show that, compared with the average AC breakdown field strength, the rate of continuous-rising voltages, from 2 kV/s, 0.5 kV/s to 0.1 kV/s, has a much greater impact on the DC breakdown strength. Besides, with the increase of step duration from 2 min, 6 min to 15 rain, the AC breakdown strength decreases slightly, while the DC strength increases remarkably. In general, with the increase of time, AC breakdown strength decreases and the DC breakdown strength increases, which lead to the continuous increase of the DC/AC ratio, from 1.33 to 3.73. Based on the lower confidence limit of breakdown strength under the confidence level of 95%, the one-hour breakdown strengths of XLPE samples are 89.50 kV/mm and 247.55 kV/mm, and the voltage endurance coefficients fitted by the in- verse power law are 17 and -11.51, respectively, for AC and DC. For the DC breakdown experiments carried out by applying high voltages in a short time, the relationship between the breakdown strength and time does not conform to the traditional electrical-aging life law. This phenomenon may be related to the time-dependence of space charge effect, which needs further confirmation by the following research work. It is also suggested that the short-time breakdown test data based on sheet samples under high voltages can not effectively reflect the long-term electrical-aging performance of DC insulation, and thus can not be directly applied for the insulation design ofXLPE DC cables.

关 键 词：现役交流XLPE电缆 绝缘切片 击穿试验 直流电压设计 电老化性能 

分 类 号：TM247[一般工业技术—材料科学与工程]