The future generation of the electrical network is known as the smart grid. The distribution domain of the smart grid intelligently supplies electricity to the end-users with the aid of the decentralized Distribution Automation (DA) in which intelligent control functions are distributed and accomplished via real-time communication between the DA components. Internet-based communication via the open protocols is the latest trend for decentralized DA communication. Internet communication has many benefits, but it exposes the critical infrastructure’s data to cyber-security threats. Security attacks may not only make DA services unreachable but may also result in undesirable physical consequences and serious damage to the distribution network environment. Therefore, it is compulsory to protect DA communication against such attacks. There is no single model for securing DA communication. In fact, the security level depends on several factors such as application requirements, communication media, and, of course, the cost.There are several smart grid security frameworks and standards, which are under development by different organizations. However, smart grid cyber-security field has not yet reached full maturity and, it is still in the early phase of its progress. Security protocols in IT and computer networks can be utilized to secure DA communication because industrial ICT standards have been designed in accordance with Open Systems Interconnection model. Furthermore, state-of-the-art DA concepts such as Active distribution network tend to integrate processing data into IT systems.This dissertation addresses cyber-security issues in the following DA functions: substation automation, feeder automation, Logic Selectivity, customer automation and Smart Metering. Real-time simulation of the distribution network along with actual automation and data networking devices are used to create hardware-in-the-loop simulation, and experiment the mentioned DA functions with the Internet communication. This communication is secured by proposing the following cyber-security solutions.This dissertation proposes security solutions for substation automation by developing IEC61850-TLS proxy and adding OPen Connectivity Unified Architecture (OPC UA) Wrapper to Station Gateway. Secured messages by Transport Layer Security (TLS) and OPC UA security are created for protecting substation local and remote communications. Data availability is main concern that is solved by designing redundant networks.The dissertation also proposes cyber-security solutions for feeder automation and Logic Selectivity. In feeder automation, Centralized Protection System (CPS) is proposed as the place for making Decentralized feeder automation decisions. In addition, applying IP security (IPsec) in Tunnel mode is proposed to establish a secure communication path for feeder automation messages. In Logic Selectivity, Generic Object Oriented Substation Events (GOOSE) are exchanged between the substations. First, Logic Selectivity functional characteristics are analyzed. Then, Layer 2 Tunneling over IPsec in Transport mode is proposed to create a secure communication path for exchanging GOOSE over the Internet. Next, communication impact on Logic Selectivity performance is investigated by measuring the jitter and latency in the GOOSE communication. Lastly, reliability improvement by Logic Selectivity is evaluated by calculating reliability indices.Customer automation is the additional extension to the smart grid DA. This dissertation proposes an integration solution for the heterogeneous communication parties (TCP/IP and Controller Area Network) in Home Area Network. The developed solution applies Secure Socket Layer in order to create secured messages.The dissertation also proposes Secondary Substation Automation Unit (SSAU) for realtime communication of low voltage data to metering database. Point-to-Point Tunneling Protocol is proposed to create a secure communication path for Smart Metering data.The security analysis shows that the proposed security solutions provide the security requirements (Confidentiality, Integrity and Availability) for DA communication. Thus, communication is protected against security attacks and DA functions are ensured. In addition, CPS and SSAU are proposed to distribute intelligence over the substations level
