As information technology (IT) advancement drives utility operational data communications towards Ethernet networking, protective relay engineers find that their telecommunications or IT departments are transitioning from legacy teleprotection channels like utility-owned TDM SONET multiplexers and rings or leased paths to Ethernet packet-based wide-area networks (WANs) based on Multiprotocol Label Switching (MPLS) routing technology.
SDG&E® began its migration to Ethernet MPLS communications for mission-critical operational uses in 2016 with the goal of incorporating teleprotection, SCADA, and time-synchronized measurement transport on a common IT-OT Ethernet network. SDG&E has many transmission circuits with line current differential (87L) teleprotection, which had utilized a private SONET multiplexer array. SDG&E worked with multiple teams of technical experts to test MPLS Ethernet based communications for 87L and directional comparison
teleprotection in their laboratory environment, with focus on meeting the channel performance demands of 87L. They presented the development and testing program in a 2017 WPRC paper[1].
Packet routing in an Ethernet WAN is less predictable than the deterministic march of data bits in TDM or serial data transmission. MPLS network latency or time delay variations raise concerns for protective relaying applications. Line current differential protection (87L) is the variant of teleprotection with the most stringent real-time communications requirements between line terminals – low delay, low asymmetry between delays in the two directions of packet exchange, and low jitter of latency. High latency slows tripping; asymmetry and jitter reduce 87L security margin and cause risk of misoperation.
In 2024 SDG&E has transitioned the bulk of its transmission lines with 87L teleprotection to its growing private MPLS Ethernet operational WAN. This paper summarizes and builds on the previous WPRC presentation with practical experience on availability and performance of MPLS teleprotection channels. We discuss MPLS network design and configuration considerations as tested, along