Realization of Line Current Differential Protection over IP-based networks using IEEE 1588 for synchronous sampling

Line Current Differential Protection is an increasingly important protection scheme due to the fast and absolutely selective detection of faults. The essential part of the Line Current Differential Protection, also known as 87L protection according to ANSI/IEEE C37.2-2008, is the communication and the related time synchronization for synchronous sampling. A widespread and well established technology for this application is Synchronous Digital Hierarchy (SDH) which is based on Time Division Multiplexing (TDM) technology. Due to the development and widespread use of Packet Switched Networks (PSN), e.g. Ethernet networks, it is already more cost effective using this communication technology instead of SDH. The underlying principle of Ethernet is packet switching which works contrarily compared to TDM networks. In this paper, a novel 87L protection scheme is proposed. The protection data exchange is realized by using IP-based communication for data transfer and an improved IEEE 15882008 Precision Time Protocol (PTP) is used to establish synchronous sampling.