## 6 Conclusions  
This paper has surveyed the key issues concerning electrical microgrids and Wireless Sensor and Actuator Networks, and its combination in order to transform the classical electrical grid into a Smart Grid. MGs are a new electrical grid paradigm that includes innovative management systems because of their particular characteristics: high renewable energy penetration, presence of energy storage systems, risk of power unbalance, and the most important issue, islanding. In order to assure a correct management of a MG, it is necessary to implement a set of sensors and actuators, which need a communication system to transmit the measured data and the command messages. Thus, Wireless Sensor and Actuator Networks are a promising solution to support the management of a MG, in an intelligent manner. In other words, MGs become more intelligent thanks to the application of WSANs and communication protocols. Even more, MGs can be seen as the first step to offer some level of intelligence to the grid; that is, to achieve a Smart Grid.  
A three-level hierarchical centralized management system for MGs has been presented, along with other decentralized solutions. Each model offers some advantages and drawbacks. Centralized systems are simpler to implement than decentralized ones, but they present an architecture that is less resistant when facing potential failures. Consequently, mixed solutions combining the two approaches seem to be a good tradeoff. In any case, a WSAN will be necessary to complete the MG management system.  
Moreover, WSANs can be also applied to manage the electrical grid at different levels: power generation, transport and distribution lines and, finally, end users and DSM. However, the needs of each stage are not exactly the same in terms of data rate, latency and reliability. Indeed, the kind of WSAN to be applied may not be the same. In that case, it will be necessary to find solutions to assure the interoperability among the different networks.  
Concerning the communication technologies to be used, it is important to identify the network level where the WSAN will be placed. Usually, WSANs are deployed in sites that correspond with HAN or NAN levels. This fact limits the choice of the communication protocol in terms of coverage. On the other hand, the power consumption caused by the protocol must be as low as possible because it will be employed by nodes limited in terms of power supply. There are several protocols that match this important requirement, with ZigBee as the most usually employed. Nevertheless, in some cases, it is necessary to adapt the existent protocols to the real needs of each application.  
Finally, some concerns related to the evolution of the grid toward a SG have been presented. It will be necessary to adapt the WSANs physical components to the harsh environment of the electrical grid, and also the security procedures in order to face the new vulnerabilities that will appear. The future SG will be able to integrate plenty of intelligent users and equipment, such as MGs with renewable energy, or PHEV, which will actively participate in the whole management of the network. In addition,the SG will become a multi-generation scenario, more energy-efficient but, at the same time, more difficult to manage. As has been pointed out, assuring the convergence and the correct operation of the different actors that constitute the SG is the real challenge that must be overcome.  
[PERSON] was responsible for the writing of Sections 2 and 4 and the Conclusions, and also collaborated in the reduction of Section 3, and the Introduction. [PERSON] was responsible for the redaction of Section 3 and collaborated in the redaction of Sections 4 and 5. [PERSON] was responsible for the redaction of the Introduction and Section 5. Finally, [PERSON] was in charge of the global coordination of the different sections and also collaborated in the elaboration of the bibliography.  
The authors declare no conflict of interest.