Demand patterns for energy consumption are changing faster than ever. Two-way power flow is changing the game, driven by renewables like solar and wind generation, as well as distributed energy resources like energy storage, electric vehicles and community grids.

These changes will fundamentally and structurally change the energy sector. This evolution will require contemporary transmission network operations be leveraged across the electrical distribution network, create new opportunities for business models, allow consumers to monitor and manage consumption closer than ever, and allow for the market to deliver new and enhanced services to customers.

In today’s mission-critical environment of real-time data transfer, communication is essential to keeping the lights on. As transmission and distribution network operators (TNOs and DNOs) offer greater reliability, more sustainability and better customer service — communications will enable them to be more efficient and effective at providing service.

This will require a more reliable communications path to carry important information and, often, critical data about the electric distribution network. This data can be used for network stability, safety, emergency operations and even disaster recovery, meaning it must be delivered promptly, securely and without risk of competing with less critical information.

The amount of data being generated is continually increasing, and for the data to be useful it must efficiently make its way to a control system. This generally has been accomplished via distributed radio frequency (RF) systems. While DNOs have used licensed field area networks (FAN) for years, the new DNO use cases are exceeding the capacity and performance of legacy networks; increasing the demand for RF spectrum and systems that are scalable to meet future system requirements.

The Difference Between Licensed and Unlicensed

Across the U.K., RF spectrum is a finite, and thus scarce, resource that is regulated by the Office for Communications (Ofcom) to be used for the public good. The spectrum is broken into bands, with each designated for a specific use. For an unlicensed spectrum, these bands can be used by anyone as long as some general rules are followed, like using an Ofcom-approved device and keeping the transmit signal level low so that transmission signals are not broadcast to a large area.

Controlling the broadcast transmission range is a key point for unlicensed spectrum because you are experiencing interference from others and introducing interference to others using the unlicensed spectrum. DNOs evaluating using an unlicensed frequency spectrum to operate their FANs are considering spectrum that is available for anyone to access and use.

In addition, the spectrum is likely used for more than just DNO applications; it also can be used for common household conveniences. These systems have been designed with transmission techniques that attempt to avoid interference, such as using frequency-hopping patterns to continuously move around small bands of spectrum or by retransmitting the data upon discovery of interference.

Due to the noise caused by others using the same unlicensed spectrum, the receive level of the signal must be stronger compared to radios operating in licensed spectrum bands. Combined, the limited transmit power and strong signal needed at your receiver means that communication is achieved over relatively short distances, sometimes as little as over a single neighbourhood.

For applications such as network sensors, where higher device density exists, this strategy is great for allowing many users access to the same spectrum. To get these messages from the closest radio device to the control center, these network designs ultimately result in end-device messages being stored and forwarded many times from radio hop to radio hop, which can result in operators waiting, sometimes many seconds, for status or the execution of commands. Even worse, these systems can time out, which results in multiple retransmissions, thereby adding increased and unpredictable delay and jitter to the network and to control applications.

Unlicensed FANs can introduce ongoing maintenance tasks and introduce frustration to the DNO end user due to the unpredictable nature of when and where service-impacting interference occurs. Interference may not exist during design and initial implementation but can crop up over time, forcing a partial redesign to optimise the network by adding repeater locations, for example.

Conversely, most licensable spectrum is reserved and used for systems or applications dedicated to a single use and in which the operator has sole and exclusive use of band across a geographic area for a licensed time period. Ofcom keeps a record of licensed spectrum requests that have been granted and has a technical procedure for preventing and/or resolving interference between licenses. If a band of spectrum has been granted for a specific application, such as DNO multiple address data nodes, DNOs can access the spectrum by filing for a license and paying a nominal administrative fee. In the UK, the Joint Radio Company (JRC) — an industry-owned spectrum management organisation — manages certain critical national infrastructure communications bands and represents its users to Ofcom.

While getting a spectrum license can be particularly challenging, as it takes time and costs money, when considering the overall operating costs, the consistency that network operators get from having sole and exclusive use makes it worth the effort. Although the benefits of licensed networks are clear, Ofcom (likely in conjunction with Ofgem) could do more to enable network operators in their pursuit of spectrum for enabling future applications.

The Last Mile

Communications have always been a critically important component for monitoring and controlling the power network. As transmission and distribution networks have naturally evolved and gotten smarter over time, DNOs have deployed remote control and collected status and alarm data from the distribution network, also known as the last mile.

Leading-edge communication networks support network operators to modernise their infrastructure to cope with today’s changing energy demands. DNOs are deploying smart devices on distribution poles and even on houses to monitor and provide remote control of plant and equipment as far as the electricity network will reach. The problem is that the distribution network and customers’ homes aren’t connected to the same private networks that the power plants and transmission substations are already using.

New private infrastructure from the last mile network devices to the already-connected power plant or substation requires stringent reliability and security. Therefore, the last mile is often reached by a radio communications technology using licensed radio networks. As the amount of data needed increases in places that are not already connected to the rest of the network, the use of licensed radio networks — instead of unlicensed — should be the first port of call for network operators.

Choosing Licensed Networks

For years, licensed radio communication has been the choice for DNO last mile communications networks for DA. This is primarily due to the secure and consistent environment in which the systems have to operate. Lately, a more technically demanding communications network is required because several factors have changed:

  • The quantity of connected devices continues to increase.
  • The amount of information that needs to be collected from each device has increased.
  • Faster communication is required for all devices (i.e., latency decreases).
  • Throughput requirements have grown for modern applications (i.e., faster speeds — 9.6 Kbps vs. 5 Mbps).
  • Security requirements have increased.

Countless licensed options on the market provide DNOs a solution to the changing communication dynamics in the last mile. Licensed networks provide:

  • Consistency and improved reliability, due to the licensed band being free from other potential interference sources.
  • Improved range, because a stronger signal can be transmitted and achieve greater receive sensitivity because the band is free from noise created by interference from other parties, resulting in overall performance in throughput speeds and latency.
  • Increased security.

By obtaining a private, licensed spectrum, network operators can benefit from a communication network which is consistent, secure and matches the reliability of the electricity network it monitors and controls.

 

As the U.K. electricity network evolves to a platform that can handle both production and consumption assets, communications systems must be increasingly sophisticated.

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Jonathan Conway is a senior electrical engineer and project manager specializing in telecommunications and network engineering with over 15 years of experience. He serves as project manager and lead engineer on various utility projects related to radio frequency design and construction, communications tower construction, network architecture and design, supervisory control and data acquisition (SCADA), and systems engineering/integration.