Accuracy evaluation of delivered measurements to HMI in a real SCADA automation system

Data transmission between RTUs (Remote Terminal Unit) and HMI at control center in SCADA (Supervisory Control And Data Acquisition) automation system is accompanying with delays due to several reasons such as: limitation in data transmission rate, distance between RTU and control center, traffic of communication network and the time needed for data modulation and processing. These delays can cause errors in delivered measurements to the HMI at control center. This paper evaluates how these communication delays can affect the accuracy of transmitted measurements as viewed by HMI in automation system of a real power distribution network. Experimental measuring has been performed to obtain the time delays in data exchange between RTU and HMI. A stochastic model, based on the obtained experimental results, is then employed to model the data transmission delay for that real automation system of power network. It will be shown how the accuracy of delivered measurements to HMI will change depending on the change rate in power network conditions when there are delays in data transmission network of the SCADA automation system.