## 1 Introduction  
### Motivation of the Research  
Due to the increasing need for distribution automation, the monitoring and control concepts integrated into modern electric distribution networks (EDNs) have significantly changed from manual to digital in the past few years [1]. Such a challenge has led to the accelerated transition of the smart SCADA (supervisory, control, and data acquisition) system, a computer-based system to monitor and control the various components of the EDNs. During the late 20 th century, the EDNs started incorporating the SCADA system. This type of system comprises various components, such as sensors, communication units, and programmable logic controllers. The EDNs incorporate multiple problems, such as power interruptions caused by weather conditions and equipment failure. A SCADA system is a tool to manage these networks to improve their efficiency and reliability. The functions of a SCADA system are carried out by collecting and analysing data from various sources such as power devices, circuit breakers, and remote terminal units (RTUs). These data are then processed and sent to a control centre. When an outage occurs, the system sends an alarm to the operators [2]. Although most electric distribution networks can integrate the SCADA system, the Distribution Network Operators (DNOs) cannot fully incorporate all of them due to the high investment requested. This economic aspect could be the main reason for partially integrating the SCADA system into the electric distribution network. The \"Distribution System Operators Observatory\" report performed by the Joint Research Centre [3] provided a status about the integration degree of automation and remote control performed by the SCADA system at the level of the high voltage/medium voltage (HV/MV) and medium voltage/low voltage (MV/LV) EDSs, which emerged from a survey carried out at 45 DNOs from EU countries. Figure 1 presents the integration status in the SCADA system in the MV/LV EDSs, considering the study's results presented in [3]. The brown circles in the figure signify the percentage of MV/LV EDSs integrated into the SCADA system. The data analysis highlights an integration degree of 30% at most DNOs (93%). Only 3 of 45 DNOs (7%) have exceeded this value. The DNOs can use the SCADA system to monitor and control various system elements, such as power transformers, electric lines, etc. With the help of data acquisition capabilities, it can also provide significant insight into the operation of the power system. SCADA systems are commonly used on the distribution side to automate the various components of the networks. They contain the following in their structure: a remote terminal unit (RTU), a master control centre, and a telecommunication network. All European DNOs use the SCADA system, which includes one or more functions: substation control, feeder control, or end-user load control (see Figure 2). The data from the figure were from a survey carried out at the level of 56 DSOs from European Union countries and synthesised in the \"Distribution System Observatory 2022\" report [4] published in 2023. Of the total DNOs representing the base of the study presented in the study [3], 70% utilised a SCADA system for end-user load control. Among the DNOs that use this function, 62% utilised a similar system for remote load control and generating bills, and 76% for an automatic metre reading. Figure 1: The integration degree of the MV/LV EDSs in SCADA system. State estimation is a prerequisite for implementing various applications in EDNs, such as increasing energy efficiency through minimising power losses, voltage control, or security analysis [5]. The EDNs have a significant number of MV/LV EDSs, which means that the total measurement infrastructure represented by the RTUs integrated into the SCADA system requires high investments. Unfortunately, it is impossible to fully monitor the state variables (voltages, power flows, injected, or requested powers) of an EDN at this stage of development.