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

Abstract

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.

Description

technical field [0001] The invention relates to the field of insulation fault detection of electric equipment, in particular to an online monitoring method for high-voltage XLPE cables. Background technique [0002] In recent years, with the continuous development of the cable industry at home and abroad, researchers have developed a variety of monitoring and detection methods for XLPE power cables, some of which have been applied in operating units. [0003] (1) External capacitive coupling sensor [0004] The structure of the external capacitive coupling sensor is shown in Figure 1(a). A pair of electrodes are installed on both sides of the cable joint (the shielding layer in the middle of the joint is separated by an insulating gasket), and the two electrodes are connected by a detection impedance. Its equivalent circuit is shown in Figure 1(b), in which C 1 、C 2 is the equivalent capacitance formed by the metal shielding layer and the core conductor, C 3 、C 4 is the...

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Problems solved by technology

[0016] ① The external capacitive coupling sensor is interfered by external noise, including broadcast signals, white noise signals, and line harmonics, and the operating environment is harsh after installation, especially on direct-buried cables that cannot be used for a long time; Cable joints and terminals laid in tunnels have poor anti-interference performance and are often interfered by corona discharge; ③Ultrasonic detection method has low sensor sensitivity due to the rapid attenuation of the ultrasonic signal in the cable; ④Ultraviolet detection method can only detect cables Discharge signals on the surface of the terminal are helpless for defects inside the cable accessories; ⑤The optical detection method is still in the laboratory research stage, and there is still a distance from practical application, and this method is difficult to achieve online monitoring

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