高压直流陆缆及海缆用大截面型线导体纵向阻水方式研究及验证

Study and Verification of Large Section and Longitudinally Water-blocking Heteromorphic Conductor for HVDC Land and Submarine Cable

为了确定最优的阻水填充材料和阻水方式,以开发高压直流陆缆及海缆用大截面纵向阻水型线导体,分别对选用的半导电阻水带和阻水胶进行阻水效果测试,并模拟电缆生产过程中导体受热情况进行了250℃下的热重性能测试(TGA),最后分别在2 MPa水压下作用10 d时间及1 m水柱下进行10次热循环的测试条件下对填充阻水带和阻水胶的3 000 mm2型线导体绝缘线芯开展纵向透水试验。阻水效果测试表明,阻水带膨胀速率和膨胀高度分别为11.5 mm/1 min及15.5 mm/5 min,均满足JB/T 10259—2014的要求;固化阻水胶在不同水压下浸泡一周后形态仍保持稳定。热重性能测试(TGA)结果显示:阻水胶和阻水带在测试条件下均未出现明显的重量损失,热稳定性能均满足电缆的生产需要。纵向透水试验结果表明:阻水带型导体在2 MPa水压作用下10 d时间的测试条件下透水距离为7.2 m,在1 m水柱下进行10次热循环的测试条件下透水距离为0.9 m,而阻水胶型导体在上述2种条件下均发生了全部长度的透水。通过检查样品发现:阻水胶型导体各层单丝外表面虽然附着了阻水胶,但是同样可见较多水珠,最可能的原因为单丝绞合时阻水胶的填充工艺不完善,从而造成阻水胶型导体内存在供水分沿纵向渗透的通道。阻水带型导体铜单丝缝隙中有大量膨胀后的阻水颗粒分布,阻止了水分纵向渗透,因此可以满足高压直流陆缆及200 m及以下水深直流海缆工程的使用需要。

To confirm the best water-blocking material type and the way of being filled to develop large section and lon- gitudinally water-blocking heteromorphic conductor, we experimentally investigated the water-blocking effect of the chosen water-blocking tape and absorbent thixtropic gel by thermal gravity analysis （TGA） at 250 ℃ according to the heating environment of production status of HVDC cable. Then a longitudinally permeable test on the insulated conductor in 3 000 mm2 was porformed under the conditions of 2 MPa hydraulic pressure for 10 days and 1 m water column with thermal cycle in 10 times, respectively. The results of water-blocking effect test showed that the swelling rate of wa- ter-blocking tape was 11.5 mm/1 min, and the expansion height was 15.5 mm/5 min, which both met the requirements of JB/T 10259--2014. After being dipped in the water with different hydraulic pressures for a week, the form of absorbent thixtropic gel was still stable. The weight of both water-blocking tape and absorbent thixtropic gel after TGA did not sig- nificantly change, revealing that the thermostability could meet the requirements of cable manufacturing. For heteromorphic conductor filled with water-blocking tape, the longitudinally permeable distance was 7.2 m under the con- dition of 2 MPa hydraulic pressure for 10 days, and the longitudimally permeable distance was 0.9 m under the condition of 1 m water column with thermal cycle in 10 times. The heteromorphic conductors filled with both absorbent thixtropic gel and water-blocking tape were fully penetrated during the longitudinally permeable test. By checking the sample, so- lidified absorbent thixtropic gel was adhered to the surface of single line tightly, but there was also drop of water. The most possible reason was that, there was a passageway for water to permeate through due to the defective incomplete processing. Plenty of intumescent water-blocking particles distributed in the gap of single line of heteromorphic conductor filled with water-blocking tape, which caused a good longitudinally water-blocking performances. Therefore, the hetero-morphic conductor filled with water-blocking tape could be used for HVDC land cable and submarine cable in water with a depth of no more than 200 m.