For a long time, China's power system executes the periodic maintenance to the electrical equipments, that is, equipment testing and maintenance will be carried out according to the planned time period, thus causing the defects of the excessive maintenance and inadequate maintenance. With the new change of the form for the power equipment defects, on-line monitoring of the partial discharge and on-line monitoring of chromatogram, SF6 gas quality began to increase. State Grid Corporation of China clearly put forward, from 2010 onwards to comprehensively promote the implementation of equipment condition maintenance, and comprehensively enhance the level of intelligent equipment and promote the use of intelligent equipment and technology, achieving online early warning of power grid safety and intelligent supervisory control of equipment.

Take the main on-line monitoring system of the primary equipment of transformer substation for example, there are: On-line monitoring of capacitive equipment’s capacitance and dielectric loss; on-line monitoring of the full current and resistive current for the metal oxide arrester; On-line monitoring for the ontology insulating oil chromatogram of the transformer; on-line temperature measurement of the optical fiber; On-line monitoring for partial discharge of ontology ultra-high frequency; on-line monitoring for partial discharge and dielectric loss of casing pipe; on-line monitoring of dynamic property for load switch; on-line monitoring of GIS UHF PD (ultra high frequency partial discharge); on-line monitoring of micro-water; on-line monitoring of switch mechanical characteristics and on-line monitoring of the fiber-optic temperature for switchgear, SF6 gas density on-line monitoring etc.

From the " Report Preview of Industrial Competiveness Analysis on China's Power Equipment Industry," the material shows, the market of online monitoring products is mainly concentrated in the power transmission segment of the smart grid. In the smart power grid planning report, State Grid Corporation of China has also taken the construction of substation condition monitoring system as an important content of intelligent substation. Through the condition monitoring unit, the Intelligent substation can achieve the partial discharge of the transformer oil chromatography and composite apparatus, online monitoring to the full current of lightning arrester and other major equipments as well as the important parameters, providing the basic data support for power grid equipment management. Real-time status information is analyzed and processed by the expert system, which can make a preliminary decision, achieving self-diagnostic features of the intelligent equipment within the substation.

In 2012, State Grid Corporation firstly put forward the concept of intelligent power transmission line, promoting the online monitoring from the substation side to the line side, so as to mainly monitor the vertical arc of the electric transmission line, the pole and tower against the invasion of external forces, micro-weather of line segment etc. The data transmission can be conducted by OPGW optical network or wireless public network. In the remote area, carrying out the real-time analysis to the electric transmission line status, realizing the advanced applications of dynamic capacity.