Connection Time in Modbus/TLS for Secure Communications on Photovoltaic Systems

The growth of Renewable Distributed Generations (RDG) presents both, a solution to common problems of traditional energy sources - such as the environmental impact and losses in transmission and distribution - and a challenge to appropriate control a large number of Distributed Energy Resources (DERs). The feasibility of such control depends on adequate communication protocols that, among other features, need to address the security requirements of DER applications. Modbus/TLS was presented in previous work as a possible protocol for direct DER communications and analyzed with respect to bulk data transfer. This paper extends such analysis, evaluating the connection time for multiple key exchange algorithms configurations, discussing possible impacts and proposing alternatives for environments where the observed connection times are prohibitive.