混合排列方式对双回路XLPE电缆护层环流的影响

Effect of Mixed Arrangement on Current in Sheaths of Two-circuit Arranged XLPE Cables

为有效降低双回路电缆金属护层的环流,提高电缆的使用寿命和载流量,分析了混合排列方式对双回路交联聚乙烯（XLPE）电缆护层环流的影响。首先,根据电磁学理论,推导了双回路XLPE电缆金属护层环流的计算过程;然后利用自制程序,分析计算了220 kV单芯XLPE电缆采用水平、直角混合排列方式时的护层环流值。研究结果表明：交叉互联分段均匀的情况下,电缆混合排列时的最大环流值将达到负荷电流的14.4%;而400 m-500m-600m分段的情况下,混合排列方式下电缆护层的环流值可达到负荷电流的24.2%,超出了工程允许范围。另外,相同敷设条件下,单回路电缆护层的环流比双回路敷设情况要小30%左右。为抑制XLPE电缆护层的环流,应严格保证交叉互联单元内电缆的排列方式一致,并尽量保证3小段的电缆长度相等。

In order to reduce current in metal sheaths of crosslinked polyethylene（XLPE） cables, and to increase the service life and ampacity of cables, we analyzed the effect of mixed arrangement on current in metal sheaths of two-circuit arranged XLPE cables. Firstly, on the basis of the theory of electromagnetism, a process of calculation of current in metal sheaths of two-circuit arranged XLPE cables was deduced. Secondly, the value of current in sheaths of 220 kV single-core cables, which were laid in both horizontal and right angle form, was calculated by using a self-made program. The research results show that the maximum circulating current value of mixed arranged cables has reached 14.4% of load current when the cables are segmented evenly; under the segmentation of 400 m-500 m-600 m, the current value may be 24.2% of load current which is beyond the allowable range. In addition, the circulating currents in single-circuit cables is about 30% lower than that in double-circuit cables under the same laying conditions. In order to reduce the current in sheaths, we should make sure that the cables, which belong to the cross-bonding unit, should be arranged in the same order, and the length of segments should be equal.