## 1 Introduction
### Wide Area Network  
The Wide Area Network (WAN) connects various NANs. Data collection points are located at various places and the collected data are forwarded to central controller. The coverage area for WAN is around thousands of square miles [13; 14; 15; 16]. The requirement of data rate is around 10-100 Mbps. Wide area network requires very high bandwidth for its operation and management. WAN is suitable for Supervisory Control And Data Acquisition (SCADA) systems for monitoring, data acquisition, control and management of power grid [14; 15; 16; 17]. With the advancement in communication standards and embedded systems, wireless sensor networks have become an inevitable component of smart grid technology. They can be used to bring intelligence in power grid due to their capability to collect, store, process and communicate information [18; 19; 20; 21; 22; 23]. The layered architecture of Smart Grid in terms of national, continental and intercontinental power management is also crucial for design and deployment of interconnected networks [24]. At present, Smart Grid is the most inventive technology being explored by researchers over the world. Design and testing of communication network for Smart Grid layered architecture using Zigbee technology is discussed in [24]. Other technologies such as Wi-Fi, Wimax and Bluetooth are considered for Smart Grid communications in [22; 23; 24; 25; 26; 27; 28]. Implementation of Internet of Things (IoT) for Smart Grid is explored in [29]. Recent progress in advanced metering is depicted in [30]. Cyber security for Smart Grid infrastructure is an inevitable requirement for reliable operation of utilities. Cyber security threats and solutions for smart grid are analyzed in various studies [31; 32; 33; 34; 35; 36; 37; 38]. A critical case study on overall Smart Grid security aspects and solutions for HAN based on Zigbee technology is described by [PERSON] et al. [39]. The authors have depcted the lessons learnt from implementation of smart microgrid using personal area network based on IEEE 802.15.4 standard in University of Pisa in [39]. The relation between intricacy and security has been pointed out by [PERSON] et al. : \"Complexity is the worst enemy of security\" [40] (p. 531). The technologies and policies for alternative fuels and vehicles are discussed in [41] and [42]. Smart Grid is an interconnected, hierarchical and heterogeneous network with enormous complexities and dynamics. Thus, gigantic network architecture of Smart Grid creates many security challenges. However, the above-mentioned statement is divergent for WSN as it contains tiny sensor nodes with limited computational and storage capabilities. For WSN, simplicity of design and implementation becomes the worst enemy of its security and makes it more vulnerable to attacks. WSN is an essential component of Smart Grid communication infrastructure. Overall cyber security concerns and solutions for Smart Grid network are widely described in literature. Attacks, vulnerabilities and Security requirements for WSN are different from the overall network security essentials due to design and limitations of sensor nodes. The address specific security attacks and solutions may not be applicable for data oriented approach of WSN as communication between sensor nodes is concerned with the data rather than the address of a specific sensor node. For example, readings of humidity and temperature of a specific area can be sent by redundant nodes. Thus, the security of redundant sensor nodes should also be considered. Security of WSN is one of the most vulnerable, complicated and challenging aspects of Smart Grid security. It can be considered as a base of entire Smart Grid network security. This paper is focused on WSN attacks, detection methodologies and security aspects. It is expected to serve as a reference for design of secured sensor network for Smart Grid applications.