Insulator surface electric charge online measuring probe and measuring method thereof

The invention relates to an insulator surface electric charge online measuring probe and a measuring method of the insulator surface electric charge online measuring probe. The probe comprises an SMA connector, a shielding part, a coaxial cable and an electrometer. The SMA connector is connected with the coaxial cable through the shielding part. The coaxial cable is connected with the electrometer. The method includes the following steps that firstly, the probe is installed and forms a capacitor C2 with the tested electric charge; secondly, the input voltage U1 is regulated and the output voltage U2 is recorded; thirdly, a change relation curve between the U1 and the U2 is recorded; fourthly, as a C1 is 113pF, a C2 is calculated out through the formula in the specifications; fifthly, capacitance equivalent area A is calculated out through a capacitance computing formula with the C2; sixthly, sensitivity S is calculated out through a formula S=C1/A; seventhly, the charge density is calculated out through a formula that sigma equals to SU2. By means of the insulator surface electric charge measuring method, the safety state of the GIS can be effectively estimated and the method has a major significance in safe operation of the GIS.