211 / 2022-03-14 18:41:59

Analysis of Cable Sheath Transient Characteristics for 330-kV Line Energization

sheath overvoltage, sheath bonding method, line energization

The application of power cables shows an increasing tendency in extra-high voltage transmission lines, but there is still a lack of experience in cable design and maintenance of 330kV-rated cables in northwest China. It is of great significance to ensure that the cable outer sheath could withstand power-frequency and energization overvoltage, and the sheath voltage limiter play a protective role without failure.


A pure cable line, an overhead-cable line under construction and an overhead-cable-overhead line in operation were selected to simulate the in-ground short circuit and multiple no-load closing, and the maximum sheath overvoltage at the insulated joint was observed. After the sheath voltage limiter is determined based on the sheath power-frequency overvoltage results, it was brought into the simulation again to verify the correctness of the selection.


The sheath power-frequency overvoltage of the long-distance hybrid overhead-cable line was the severest, up to 15kV, and therefore the voltage rating of the sheath voltage limiter was required to reach 12kV. In addition, the sheath overvoltage obtained by closing the single-point grounded side was obviously larger than that of the cross-bonded side for the pure cable line. It should be noted that the sheath overvoltage of the hybrid line was significantly larger than that of the pure cable line applied with the same bonding method, which was greatly influenced by overhead line portion and number of circuits.


The power-frequency overvoltage and energization overvoltage imposed on the existing 330kV sheath bonding system was at a reasonable level for outer sheath insulations. The 8-12 kV sheath voltage limiter can be selected according to the specific line configurations to ensure the safe and stable operation of the cable outer sheath and the device itself.