Prospective Relay Protection System for Digital Distribution Networks

With the development of 6 – 35 kV digital distribution networks, the manual calculation and input of operation parameters for relay protection (RP) starts to become problematic. Since calculating the operating values may take weeks or even months when using the conventional approach, it is currently impossible to fully and promptly account for network reconfigurations, the connection of additional loads, or the presence of distributed generating facilities. This problem becomes especially pronounced in advanced smart grids, where modes and network configurations are more dynamic. Four stages of developing digital RP for 6 – 35 kV distribution networks are proposed. In the first two stages, the main and backup protection systems are upgraded to differential and relatively selective multi-parameter protection, respectively; these approaches offer a higher technical specification and greater reliability than conventional RP due to the use of IEC 61850 standard for data communication networks and multidimensional measurements. In order to define set points of backup protection, it is proposed to use automatic calculation technology, which ensures complete automation of routine relay protection, as well as the highest sensitivity and response speed, by continuously adapting settings through the data communication network. Along with the new highly sensitive multidimensional protections, previous-generation protection systems, including those based on electromechanical approaches, can be simultaneously operated on the distribution networks in any combination and quantity.