As the basis of analysis and control of the power system

state estimation is an important component part of the energy management system. According to the state estimation methods available (including weighted least squares estimation

classical robust estimation and new estimation methods that have sprung up in recent years)

this paper analyzes the main problems in current researches. In addition

it is pointed out that the introduction of set theory estimation can not only solve these problems effectively

but improve the credibility of estimation results significantly as well. Then

based on the main idea of set theory estimation

a power system state identifying model is studied. This model can define the relationship between the true state of system and the identification results

ensuring the credibility of the results. Property sets of this model are described mathematically and solution sets based on intervals are proposed

guaranteeing the solvability and applicability of this model. This work is supported by National Natural Science Foundation of China (No. 51207136).