Transitioning From Legacy TDM to High-Speed Packet Networks Seamlessly for Utilities

Utilities have been deploying their own dedicated networks to enable remote control and maintenance of the grid for decades, starting with two-way radio to today’s distribution automation applications.

From the first uses of analog microwave, utilities have been building large networks that now include fiber-optic cables and digital microwave built to be more reliable than public telecom networks. These systems include the SONET/SDH transport networks needed to reliably transmit data over various physical media via substation to substation, and substation to control center. Now utilities are actively shifting to packet-based networks, with the primary reasons being:

  • Applications are moving away from legacy serial and analog to ethernet/IP.
  • SONET/SDH networks are mostly obsolete and no longer supported, meaning spares and support are no longer available.
  • Capacity requirements are increasing due to additional applications like high-definition CCTV security cameras and distribution automation.
  • SONET/SDH networks, while they guarantee capacity for previsioned circuits, do not scale well with IP applications where statistical multiplexing and prioritization make more efficient use of network capacity.
  • Hiring and training field and engineering staff to build and maintain legacy networks is becoming more difficult as experienced staff retire.
  • Modern packet-based networks provide modern and secure management while monitoring protocols and interfaces for automating operations, as well as the potential for simplified monitoring of multiple systems from a single platform.

These issues are concerns for utilities and delaying the adoption of new technologies only exacerbates the problem as a new network deployment needs to be deliberately planned and deployed, not rushed to the field. This includes a deliberate selection of technology and a platform the utility can operate over the life of the product.

For utilities to smoothly migrate from the old time-division multiplexing (TDM) transport network to a new packet-based network, utilities must develop a strategy, capex budget, program schedule, existing network analysis, selection of vendor/platform, detailed design of the new network, and a deployment and cutover plan.

The following are important points for utilities to think of to make this transition journey a seamless experience.

  1. Network Analysis:
    It is crucial for utilities to start with an analysis of existing network infrastructure, including:
    • Existing services.
    • Interface types and protocols.
    • Current network capacity utilization.
    • Future network capacity estimates.
    • Fiber and microwave infrastructure.
  1. Reliability and resiliency requirements:
    Define the requirements for the new system based on both the new equipment and the underlying infrastructure.
    1. Path protection switching as good or better than SONET/SDH.
    2. Redundancy of CPU/controller/line cards to provide continuous operation through failures and upgrades where practical.
  1. Latency requirements:
    A detailed analysis of applications like teleprotection, and a likely focus specifically on current differential requirements, are needed to determine suitable vendor solutions, final design and implementation in the network.
  1. NMS features:
    1. Support for centralized network management station (NMS) is required to avoid manual work as well as manual command input that is more prone to human error.
    2. OAM features of newer technologies should have strong features for network performance monitoring and network troubleshooting.
  1. Legacy interface support:
    If the need for supporting RS-232/RS-485, v.24, v.35, T-1/E-1 or others is needed, such support needs to be evaluated and included in the new platform.
  1. Network synchronization:
    Utilities need a plan for synchronizing the new network with protocols like SyncE and IEEE1588v2. Both time of day and frequency distribution are needed for logging and legacy application support on the new network.
  1. Network architecture and loop avoidance methodology:
    Considerations for wide area layer 2 services or possibly the underlying transport technology itself and the necessary loop-blocking protocols are needed. Interactions with external networks as well as how the transport topology may be restricted by loop-blocking protocols like G.8032 need to be understood during vendor selection and early design.
  1. Backbone Network Capacity:
    Analyzing application requirements can be modeled and used to determine the capacity needed for the network links and backbone, i.e., 10 GigE, 100 GigE, etc.
  1. Capex and Opex:
    A careful look into long-term maintenance costs along with digging into support contracts and what licenses are required versus optional is important in controlling both the initial cost of the network and ongoing maintenance costs for the system.
  1. Security features:
    Cybersecurity is a primary concern for mission-critical networks. This means that looking at network security features, patching processes and the vendor supply chain are key tasks during a vendor selection process.

Navigating critical network systems requires hands-on experience in upgrading and designing network platforms to successfully deploy and execute projects. As utilities evolve with the ever-changing industry, finding a company that has knowledge and experience in technology verticals including IP/MPLS, MPLS-TP, Carrier Ethernet, DWDM and across many vendor solutions is crucial.

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Sagar Shingare

Principal Engineer