The real-time data collected by the SCADA system reaches the main station system through many links such as the plant-site cable, transmitter, RTU, telecontrol channel, communication patch panel, telecontrol cable, front-end machine, etc. Any abnormality in any link will affect As far as the correctness of the data, in the case of RTU crash or communication interruption, there will also be dead or bad data. It is not very reliable to directly use these measured data for real-time analysis and calculation of the power grid.
The real-time measurement system configuration of the power system generally has greater redundancy, which is manifested in the following two aspects:
1. Redundancy of measurement of bus connection components
For a busbar connected with N elements, according to Kirchhoff’s law, as long as N-1 elements are measured, the electrical quantity of the Nth element can be calculated according to the principle of busbar balance. In fact, all N elements are often measured, so that there is a redundancy of 1 for each bus.
2. Redundancy of measurement of bus state quantity and injected electrical quantity
Among the four electrical quantities of busbar state quantity (voltage amplitude and phase angle) and injection quantity (active power, reactive power), two are independent and two can be derived. Redundancy is present if there are more than two quantity measurements. The general busbar remote measurement includes the busbar voltage amplitude and the two injection quantities formed by the active and reactive power of the connected components, which has great redundancy. Some components also measure the current, which is more Increased measurement redundancy.
Power system state estimation is to use the redundancy of real-time measurement system, apply estimation algorithm to detect and eliminate bad data, improve data accuracy and maintain data consistency, and provide reliable real-time power flow data for network analysis.
The use of state estimation must ensure that the inside of the system is observable, and the measurement of the system must have a certain degree of redundancy. State estimates made in the absence of measurements are not available.