# Heterogeneous Wireless Networks for Smart Grid Distribution Systems: Advantages and Limitations
## 1 Introduction  
Establishing real-time communication among a variety of power grid components at different voltage levels has been the focus of the communication research community for a while. Power utility companies have had a successful experience with the supervisory control and data acquisition (SCADA) systems in monitoring and securing the high voltage (HV) transmission part of the grid. Communication technologies have also supported similar functions at the more component-dense distribution part of conventional power grids. However, particularly for the distribution part, smart grids expect much higher support from communication technologies. This is required for upgrading the system smart functions such as self-healing, where a system controller can take actions without human intervention. The challenge is to involve distribution systems with a large number of substations, distributed equipment/sensors, and energy resources, especially in locations where establishing a new communication infrastructure is not feasible. System grids often promote a low energy consumption and a high penetration of local renewable energy generation in order to support future smart cities with sustainability programs including smart buildings [1; 2; 3]. This requires a direct interaction of distribution system customers with energy management and conservation entities [3]. However, the increased penetration of conventional and distributed energy sources, with the dynamic involvement of energy consumers, leads to more complicated distribution systems. As a result, profound changes in grid topology and operational schemes are eventually expected to be imposed [4]. Therefore, upgrading the distribution system communication network infrastructure to allow large data analysis and real-time operation and control strategies is essential to overcoming the foregoing challenges in establishing sustainable smart cities [1; 3; 5]. The success of achieving a high level of distribution system automation, such as predictive diagnosis for self-healing applications (i.e., automatic fault detection, localization, and power restoration), heavily relies on the availability and efficiency of the underlying communication infrastructure [6; 7; 8]. Exchanging all the sensed data and commands between the primary and distribution substations should be done reliably and in real time. Reliability implies communication system availability and its ability to guarantee the delivery of data packets. The real-time requirement is addressed by meeting a certain end-to-end delay. For instance, IEEE 1646 standard [9] provides guidelines for the time constraints to communicate information between intelligent electronic devices (IEDs) for substation integrated protection, control, and data acquisition. The standard classifies messages according to their urgency. For example, the maximum message delivery time required for system protection ranges from \(\frac{1}{4}\) cycle (for applications within a substation) to 12 ms (for applications external to a substation) [9]. In light of the above, this work investigates the effectiveness of implementing HWNs by the aid of multipath transmission control protocol (MPTCP) in the communication infrastructure of future smart grid distribution networks. MPTCP uses multiple paths to deliver data simultaneously and reliably over multiple TCP subflows. This work proposes that distribution substations (either secondary or primary) be equipped with HWN-ready monitoring and control units (MCUs) with various integrated sensors. These MCUs are capable to communicate over hybrid wireless communication networks via dual-interface transceivers, supporting two different wireless technologies, and are MPTCP capable. The role of the MCUs is to collect data locally from a variety of sensors/intelligent electronic devices such as phasor measurement units (PMUs), current transformer meters (CTs) and potential transformer meters (PTs).