In terms of processing high-dimensional data for evaluating the operational status of urban power grids, this study aims to improve the accuracy and processing speed of the evaluation. Firstly, the combination of Analytic Hierarchy Process and self-coding network was used to reduce data dimensionality and simplify the complexity of model input. And improvements were made to the online sequence extreme learning machine algorithm to enhance the model's adaptability to dynamic data streams and real-time learning capabilities. These results confirmed that the reduced dimensionality of the self-coding network could effectively capture the core information of the 85 dimensional raw data. The prediction accuracy of the weighted online sequence extreme learning machine algorithm was significant. Its predicted average value of 0.0994 was almost the same as the actual value of 0.0991, which was better than the comparison between the standard online sequence extreme learning machine's predicted value of 0.0946 and the actual value of 0.0986. In addition, the weighted online sequence extreme learning machine converged faster and had higher prediction accuracy than traditional support vector machine after 450 iterations. These results confirmed that the combination of dimensionality reduction technology and dynamic update learning mechanism could effectively improve the accuracy of urban power grid state assessment. This study provides a new technical solution for real-time monitoring and fault prediction of urban power grid operation status, which is very important for ensuring the safe operation of the power grid.