For clarifying the pros and cons of the presently various measurement principles of the leakage current of the arrester

selecting the measurement principle with higher accuracy and better applicability

and solving the problem that the traditional online monitoring device is not sensitive to the early performance deterioration of the arrester and can not avoid the interference of the polluted current of the outer coat

such four current analysis methods as the full current method

the resistive current fundamental wave method

the capacitive current compensation method and the harmonic analysis method and their interference factors are analyzed in this paper. It is considered that for the AC power system at 110 kV and above

due to the small harmonic interference of the power grid

the use of the harmonic analysis method as the leakage current analysis method of the online monitoring device of the arrester is more accurate and reliable. A kind of built-in online monitoring device of the arrester based on the harmonic analysis method is proposed in this paper. The temperature and humidity as well as current sensors are built into the cavity of the arrester element

the monitoring data of the temperature and humidity of the arrester core and the leakage current are collected

and the operation state of the arrester is assessed in a multidimensional real-time manner. Compared with the traditional monitoring device of the arrester

the built-in monitoring device improves the accuracy of the measurement in terms of the design principle

has passed the operation reliability verification

and is a more effective state monitoring method.