Keeping the Lights on in the Face of the TDM Sunset

by Mark Madden, Alcatel-Lucent

Electricity is the lifeblood of modern society. It powers commerce, entertainment and essential services such as transportation, health care, public safety and more. Yet the electrical grids that support these services have relied on communications networks that have become outdated. Worse, these networks are being decommissioned-a process known as the TDM (time division multiplexing), Analog and Frame Relay Sunset. This process has the potential to introduce substantial risk to energy distribution systems throughout the U.S. and across the world.

Carriers, also known as telecommunications service providers or “telcos,” are evolving to Internet Protocol (IP) technology-the same technology that is the foundation of the Internet-to deliver all of their services. As a result, traditional landline phone networks are going away. This is a natural technological evolution to more efficient, flexible and powerful networks that can support voice, video and broadband Internet services. Economic necessity is driving the changes; the older networks are unprofitable to operate and difficult to maintain.

This would not present a significant problem except that for decades utilities have used these networks to manage some of their most critical processes, such as transmitting data from substations on the their grids and supporting applications such as teleprotection, which isolates areas of the grid if they encounter a problem to keep the failure from spreading.

Utilities must find alternatives to older communications networks quickly to support these critical capabilities. Unfortunately, the near-term options aren’t always attractive.

Let’s explore one potential impact of this move from legacy communications networks and the implications on grid stability. Take a hypothetical example of a regional utility that depends on a combination of circuit-switched and frame relay technologies to support dynamic line rating (DLR) sensors that track the characteristics of high-voltage transmission lines, including heat load and sagging, which are often signs of an impending failure. Imagine that the carrier that provided their circuit-switched and frame relay network-which, although outdated, were reliable-suddenly served notice that they planned to shut down the service within 120 days. This might sound extreme, but it is a realistic scenario. Required notice periods in many parts of the country are very short.

This utility has options, however. In this scenario, the carrier offered two alternatives: a very high-bandwidth, fiber-based Ethernet service (many times more expensive than the existing TDM/frame relay service) or mobile data service (which is less expensive than Ethernet but also less reliable than the existing service).

Utilities are regulated and can’t simply pass additional costs on to customers without permission, and the short notice period does not allow enough time to explore more creative, longer-term options. Out of necessity, the utility goes with the short-term, low-cost fix: the cellular connection to the remote DLR sensors.

Under normal circumstances, this is a workable solution and helps ensure proper grid function. But under certain circumstances, the limitations of this approach become evident. Imagine a thunderstorm brings down a few trees, creating a power outage that, while geographically limited, affects residences, businesses and the carrier’s cell tower that serves the DLR sensors. Backup batteries continue to support the connection for several hours and eventually fail, leaving the line unmonitored exactly where people were returning from work and creating peak electrical demand on the grid. The transmission lines overheat, causing the line to sag onto another tree damaged in the storm and short out.

This causes a cascade where system protection breakers are tripped at adjacent substations, which then create a surge on further substations, resulting in a regional outage across several states.

Cascading failures of this kind have happened, such as the blackout that affected sections of Ohio, New York and Canada in 2003. The cause in that case was somewhat different from the hypothetical example, but risk of this kind of failure remains real and the potential causes are many.

The best way to avoid these risks is to develop an evolution plan and begin transitioning as quickly as possible to a data networking approach that can address the unique performance and feature requirements of utilities while keeping unnecessary cost, complexity and risk in check.

Utilities can upgrade to higher bandwidth, IP-based solutions offered by their current carriers or their competitors, but these services likely will result in substantially higher operations and maintenance costs, which could become prohibitive if these expenses are replicated across an entire grid. Similarly, wireless solutions are available and can meet many utility needs, but they don’t have the same reliability and predictability as the services they replace.

Another promising option is extending the utility’s privately owned network using packet-based technologies, specifically IP/MPLS, Carrier Ethernet or both, which can support all of the features and capabilities they need on a single network. This is the same technology carriers use to deliver more advanced services. The major distinction is that the carriers don’t necessarily prioritize the requirements utilities have in service quality and traffic engineering controls. If they deploy this technology themselves, utilities can ensure that all of their requirements are addressed.

Every utility’s situation is different, and utilities face somewhat different challenges. But they all must evolve away from TDM, analog and frame relay networks. Various paths can take utilities toward that end. It’s time to plan for that evolution before they become captive of the carriers’ own evolution plans and their choices become more limited because of practical and financial pressures.

Building and maintaining a private network can become a compelling option in the face of the cost of leased services and would be a powerful approach to helping ensure the continuity of operations. This is particularly true as severe weather and power consumption spikes grow in frequency.

Deploying a new packet-based network or extending the reach of an existing network into the field takes time and careful planning. The time to begin that planning is now.


Mark Madden is regional vice president of North American utilities at Alcatel-Lucent.

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