On-line monitoring method used for high-voltage XLPE (Cross Linked Polyethylene) cable

The invention discloses an on-line monitoring method used for a high-voltage XLPE (Cross Linked Polyethylene) cable. A built-in capacitance coupling sensor induces a first discharge signal in a cable accessory, a coaxial cable is led out through a rubber plug at a seal mouth of a metal shell of an intermediate joint to be used as a signal line to transfer the first discharge signal; the first discharge signal is led out through the coaxial cable and is then processed through a filter, an amplifier, an electronic-to-optical transducer, a monitoring center and a collecting card to obtain a third discharge signal; the monitoring center processes the third discharge signal and counts the phase angle, the amplitude and the number of discharge of the third discharge signal in multiple continuous industrial frequency cycles; and the high-voltage XLPE cable is monitored according to the phase angle and the amplitude of the third discharge signal. The installation of the built-in capacitance coupling sensor does not damage the insulation structure of the high-voltage XLPE cable accessory, cannot damage the operation of the high-voltage XLPE cable, and cannot be influenced by an operating environment. The method has the advantages of simplicity in installation and convenience for calibration and is beneficial for popularization.