In order to reduce the induced overvoltage of the metal sheath of single core AAAC Cable lines of 110kV and above, a protective layer protector should be installed between the ungrounded end of the metal sheath and the earth.
In case of system trip or line lightning stroke, special patrol shall be conducted for cable sheath protector.
The valve plate of protective layer protector may be damaged during power frequency overvoltage. The damage degree of the valve plate is related to the overvoltage of the protective layer. If the valve plate is damaged, it should be replaced.
At present, zinc oxide sheath protector is widely used in high voltage ABC Cable lines, and its residual work ratio is 2.5 ~ 4.0. Insulation resistance monitoring should be carried out for sheath protector, which can usually be tested at 500V / min.
The cross transposition box should be cleaned once a year, and the underground transposition box should also be checked for ponding.
