Editor's Note: This article was contributed by Tim Wallaert, our marketing director responsible for the Energy sector.

A huge amount has been written about the “Smart Grid” in recent years and most of it leads you to believe that every substation is communicating using high-speed Ethernet between all of its various components. But let’s face it – utilities don’t replace anything until it’s absolutely necessary.

The intelligent electronic device (IED) that was installed 15 years ago to monitor the status of the transformer is still out there. No one is even going to think about upgrading that IED until it or the transformer fails. This means the outdated serial port on the IED is going to be the main way to communicate to that device for quite a long time.

This begs the question of how to incorporate serial communication devices into a modern Ethernet infrastructure. Today, we’re going to take a look at this critical, and often times overlooked, issue. 

Windfarm with Car Image

Combining old and new – today’s electrical grids must support old serial devices and
integrate new technologies, such as energy from renewable resources.

Substation Communications Trends

First, let’s take a step back and look at the two trends that have caused utilities to re-evaluate their substation communications infrastructure. One trend is the migration of the electrical grid from a reliable, but inflexible system to the “Smart Grid,” which promises adaptability and efficiency. It also requires the two-way communication of data, something that is not possible with traditional electrical grids.

The other trend is the increasing adoption by industry of Ethernet networking technologies for their communications. The ARC Advisory Group estimates that the adoption of industrial Ethernet networks is growing, on average, at about 12 percent a year.

The final “end game” would appear to be a Smart Grid solution built upon Ethernet networking technology. But getting there won’t happen overnight, leaving many utilities with the challenge of incorporating older serial communication schemes with newer Ethernet communication schemes. Hybrid schemes combining both are more common than not.

New call-to-actionWhy Incorporating Serial Communication Devices is Important

A key characteristic of the smart grid is its dependence on two-way communications. This facilitates:

  • Integrating renewable resources into the grid
  • Improving reliability by monitoring equipment and fixing problems before they cause an outage
  • Decreasing recovery time by smartly switching power around downed areas
  • Meeting peak demand without building out more traditional generating facilities

To accomplish this, the components of the electrical grid need to communicate and share data quickly. This is why Ethernet networks and communication equipment are being installed in substations, it enables the two-way communication of data. This is a colossal modernization and all cost efficiencies are important.

Thus, maximizing the useful life of legacy IEDs and other serial communication devices by connecting them to modern Ethernet networking infrastructure is an important cost saving strategy. It not only extends equipment life, but can significantly reduce the cost of upgrading to a communication system that is Smart Grid “ready.”

The Secret to the Hybrid Communication System: Terminal Servers

So, here’s the challenge – there is (or will be soon!) an Ethernet communication infrastructure somewhere in the substation connecting the newer IEDs (with built in Ethernet) to a switch or router with a connection to a larger Ethernet wide area network (WAN).

How do you get the legacy serial devices connected to this Ethernet network?

The key device that does the job is the terminal server. Simply stated, serial communication comes in one port and leaves as Ethernet out of another port.

In the substation, there is almost always the need to then route the signals. That’s why Belden’s terminal server products are also routers.


Terminal servers connect serial devices to Ethernet networks. The GarrettCom Magnum products do double duty by also routing the signals. See the entire network in this Popular Configuration diagram.

There are three main terminal servers/routers in Belden’s GarrettCom product line.   

  • The 10RX is the top of the line router, supporting up to 10 Gigabit fiber ports in addition to up to 32 serial ports. It also supports advanced security features and includes a firewall.
  • If you don’t need all of the Gigabit fiber ports, but still need a lot of serial connections then the 10XTS is your best bet.
  • Lastly, many substations only have a few devices to connect – a couple of serial ports and a couple of high-speed Ethernet ports. In this case, the DX940 is the best way to go.


Table 1: The GarrettCom product line includes three levels of terminal server/routers.
For complete specifications for each product, use the links provided in the Related Links section below. (Click here for larger image)

Substation Communications Design Best Practices

At the beginning of the article, we mentioned that integrating serial communications into the Ethernet infrastructure was a critical step in the substation communication design. Now that you know how to do that, how do you build the rest of the network?

Don’t worry. At Belden, we have been privileged to help numerous utilities deploy communications in their substations. Along the way, we’ve developed a series of “best practices” that we’ve observed. We’ve pulled them altogether. If you are interested in learning more, download the white paper featured below.

Does anyone have any stories of really old serial devices out there? If you do, please share your story with us.

Related Links