To improve the power quality of the power grid, it is necessary to accurately monitor and analyze the power quality, measure the power quality level of the power grid, and analyze and judge the causes of various power quality problems, so as to provide the basis for the improvement of power quality.

In modern power system, great changes have taken place in the structure of power load, and a large number of nonlinear, impact and fluctuating loads are distributed, such as high-power voltage regulation and frequency conversion equipment, steel-making electric arc furnace, electrified railway, large-scale rectification equipment in chemical industry, induction heating furnace, etc, The probability of three-phase unbalance is greatly improved, which affects the power quality of the power grid.

In order to achieve the overall goal of comprehensive coverage of power quality indicators, online power quality monitoring system should meet the requirements of wide application coverage and large amount of basic data integration.

Before the construction of the system, there is no on-line monitoring ability of reliability index. The basic data of reliability is mainly manually entered, and the index statistics adopts the post evaluation mode. The power quality online monitoring system needs to realize the automatic collection of power supply reliability events, and also needs to ensure the stability, timeliness and accuracy of event collection.

Data integration is difficult. As the basic data of power quality online monitoring and analysis involves dispatching, transportation inspection, marketing and other business departments, power quality online monitoring system needs to integrate and share the data of multiple business systems. However, due to the different level of information system construction and the different versions of similar systems, the data of corresponding sources are quite different and the integration is difficult.

Computational processing needs are complex. The online assessment module of power grid security risk in the system undertakes a variety of risk analysis calculation and assessment management functions in the system. It needs to calculate and analyze the data of national power grid, regional power grid, province (city) and prefecture level power grid. The voltage level covers 1000kV to 110 (66) KV. The power grid has a huge scale, high computational complexity and many calculation times. In peak hours, the number of complex business modules being called is increasing rapidly. Risk assessment first needs to scan the power flow of the whole network, so that the response time of business modules is difficult to meet the needs of users.