The remote terminal unit (RTU) is the main measurement terminal in power grids, but its measurements lack a unified timestamp, has low update frequency, and is affected by uncertain transmission delays. In contrast, the phasor measurement unit (PMU) offers high synchronization and accuracy, and has become an important data acquisition device in modern power systems. To enable coordinated use of these two types of measurement data, this paper first summarizes the sources of RTU non-synchronous measurements and analyzes the influence of non-synchronous measurement data on state estimation and power flow calculation, with supporting verification results. A measurement data correlation analysis method is proposed based on energy interaction operator. The method applies the principle of maximum correlation among synchronous data and uses the accurate data from PMU to align RTU measurements, establishing a reference timestamp for hybrid measurement systems. Simulations on the IEEE 39-node grid and a real 83-node grid in Guangdong province show that the proposed method can effectively correct the non-synchronous measurement data and improve the accuracy of state estimation and power flow calculation.