###### Abstract  
The detection and localization of faults plays a huge role in every electric power system, be it a transmission network (TN) or a distribution network (DN), as it ensures quick power restoration and thus enhances the system's reliability and availability. In this paper, a framework that supports phasor measurement unit (PMU)-based fault detection and localization is presented. Besides making the process of fault detecting, localizing and reporting to the control center fully automated, the aim was to make the framework viable also for DNs, which normally do not have dedicated fiber-optic connectivity at their disposal. The quality of service (QoS) for PMU data transmission, using the widespread long-term evolution (LTE) technology, was evaluated and the conclusions of the evaluation were used in the development of the proposed edge-cloud framework. The main advantages of the proposed framework can be summarized as: (a) fault detection is performed at the edge nodes, thus bypassing communication delay and availability issues, (b) potential packet losses are eliminated by temporally storing data at the edge nodes, (c) since the detection of faults is no longer centralized, but rather takes place locally at the edge, the amount of data transferred to the control center during the steady-state conditions of the network can be significantly reduced. fault detection; fault localization; edge-cloud framework; distribution network; smart grid +
Footnote †: journal: Applied Sciences  
1  
Dept. of the ACM/ACM Computing Research Group, ACM/  
monitoring capability in order to efficiently keep track of the grid's performance, identify possible critical areas, monitor and control two-way power flows, energy consumption and generation, grid topology, etc. [6]. An overview of measurement technologies (power sensor, smart meter, phasor measurement unit, power quality monitor, digital fault recorder etc.) used in DNs is presented in [7] together with a reporting rate of each device. The necessity for installing additional devices with monitoring, control and protection capabilities in the context of active DNs is clear, whereas the communication solution supporting it is not that straightforward. In contrast to TNs, which are generally equipped with fiber-optic cables, DNs rarely contain any dedicated connectivity infrastructure. Installing and maintaining a wired communication infrastructure would impose a substantial financial burden on DSOs as the measurement locations are placed all the way down to the prosumer level, which is the reason why the usage of the already deployed public cellular networks, such as the widely available long-term evolution (LTE), is usually considered instead [8; 9]. The distinction in the available connectivity becomes evident when schemes that are already well established and used in TNs, such as the Wide-Area Monitoring System (WAMS) and the Wide-Area Monitoring, Protection and Control (WAMPAC), are being applied to DNs [10]. It is a common approach in TNs to concentrate the entirety of the data from measuring devices in the control center and process it in a centralized fashion. However, since the backbone of the aforementioned schemes is measuring devices that produce large volumes of data, the most prominent being the phasor measurement unit (PMU), the same approach might not be the best solution for DNs. Instead, public LTE networks seem to provide the most suitable communication infrastructure at present until fifth-generation (5G) networks (currently under deployment) are sufficiently widespread to cover large-scale distributed systems such as TNs and DNs. However, as presented in this paper, the usage of the LTE network instead of fiber-optic cables presents a potential reliability issue for the transmission of data from metering devices to the remote control center and can consequently lead to either unacceptable delays or even the loss of measurements.