## 3 Methodology
### Description of Representative Infrastructure  
The topology of the chosen test network, which encompasses interconnected infrastructures, is illustrated in Figure 1. The network is made up of two autonomously functioning infrastructures: the power distribution network and the communication network. Comprehensive details of each network are elaborated upon in the following subsections. It is imperative to note that there are two unique dependencies between these two infrastructures. * The reliance of the communication infrastructure on the consistent performance of the distribution network. This is due to the wireless transmitters that source their power from the Low Voltage (LV) level of the distribution system. Specifically, they derive power from LV busbars of the Distribution Transformer (DT) labeled DT1, DT2, and DT3. * The second dependency emerges from the integration of specific RTU and AMM devices within the distribution network. When these devices malfunction, they can disrupt the distribution system's operations in two potential ways: (i) directly (by hindering the ability to control switching devices), and (ii) indirectly (through failures of metering devices). It is crucial to note that the influence of AMM devices on the distribution network's operation is not taken into account for the purposes of this paper because they are exclusively utilized for metering objectives (non-direct impact). An RTU is a device within industrial control systems that facilitates the remote monitoring and control of various processes and equipment. Its architecture typically encompasses Input/Output (I/O) modules, a central processor, onboard memory, and communication interfaces tailored for seamless connectivity to an array of devices, including but not limited to sensors, reclosers, and load break switches (LBS). To enhance their resilience, RTUoften incorporates features such as backup power supplies and redundant communication channels. Nevertheless, they are not immune to faults, and have thus been neglected for the purposes of this paper. These faults, which can significantly disturb the operation of the distribution system, may be based on diverse sources including adverse environmental conditions, inherent hardware and software defects, or lapses in communication. A comprehensive understanding of these factors, coupled with insights into their potential impact on the probability of RTU failures, is imperative. Such knowledge not only bolsters system reliability, but also aids in minimizing the risk of power disruptions and streamlining maintenance strategies. In the context of the aforementioned dependency, the test network accounts for the following four distinct RTU types:  
* RTU installed in Medium Voltage (MV) switchboards at Distribution Transformer Stations (DTS), referenced as RTU1.1-4 in Figure 1.
* RTU serving as the control mechanism for reclosers on MV lines, denoted as RTU2.1-4. * RTU positioned within the High Voltage (HV)/MV substations, labeled as RTU3.1. * RTU functioning as the monitoring and command unit for section load break switches, identified as RTU2.5. In DTS, the RTU is responsible for monitoring digital states such as switch positions and door contacts. It enables remote control of feeder switches, offers direct measurement of feeders, and can detect faults within the distribution network. Moreover, the RTU assesses power quality and accumulates data from other electronic instruments present in the installation. In the context of reclosers, the RTU showcases status indicators like recloser status and door contact. It allows for both remote and local control, furnishes 3-phase voltage and current measurements, and is equipped with the capability to detect faults on power lines. Beyond these functionalities, the RTU can handle automatic operations inclusive of protective relays, reclosers, and the management of blocking conditions. For HV/MV substations, RTU plays a crucial role in bridging communication with the SCADA system.