Although more renewable energy sources connecting to the grid can help to protect our world’s natural resources, the variable nature of clean energy also brings new power monitoring challenges to legacy architectures and the transmission operators who manage them. With more renewable power being produced, transmission and grid operators around the world are examining network upgrades or are in the process of implementing more monitoring stations.
Starting in 2012, the National Grid UK started researching designs for a transmission grid throughout the British Isles that would help integrate renewable energy sources and better measure power system harmonics across 275 and 400 kV high-voltage transmission lines. This transmission system operator delivers electricity across England, Wales and Scotland, and delivers power to 30 million people via downstream distribution partners.
The impetus for the buildout was twofold: modernization and how to better monitor renewable energy transmission. The design called to move from seven monitoring stations to more than 126 substations to cover most of the UK and power feeds from all over Europe. The new monitoring platform approach includes CompactRIO embedded control systems from National Instruments (NI) on each permanent and portable substation in the network—110 and 26, respectively.
“So the phenomena that we’re looking at, specifically with power system harmonics, are exacerbated by renewable power technology that’s connecting to the grid,” says Danson Joseph, strategy competition and productivity manager at National Grid UK. “It’s not a problem we had a few years back because those sorts of technologies weren’t dominant on the grid. Now they’re becoming quite dominant.” Renewable power harmonics don’t react in a linear way with high-voltage direct current (HVDC) transmissions.
Before this current project, monitoring power harmonic data was a “hit or miss” element for National Grid UK because of speed limitations with the older monitoring design. Plus, the transmission company wanted to move away from a reactionary position when they connected a new wind power source to the grid.
“The whole idea is to do extensive studies to evaluate new wind forms and how they reacted when connected to new HVDC locations on the transmission grid,” Joseph says. “What we’re trying to achieve here is a broader continuous, real-time view of what the network looks like. We selected points on the network where things are connected, but also other points through the network where we expect there to be issues, such as a phase unbalance.”
The embedded monitoring technology at each substation allows National Grid UK to update its measurement profiles continuously and push new parameters quickly to theses substations without operators traveling to the permanent site. It only takes about 45 minutes to deploy updates with standard network speed, Joseph adds.
“One of the big selling points for us is that we can have monitors in all corners of the country and everywhere in between,” Joseph says. Each substation has one or two control and data acquisition systems, depending on the lines coming into the substation. The transmission operator chose the 1.33 GHz dual-core processor for all the control monitoring platforms with top speed and future expansion in mind.
More visibility needed
With more substation monitoring coming online, National Grid UK realized an opportunity to leverage the increased data inputs for its operators and innovate with web apps in and out of the centralized control room.
“We have a really nice little web app that presents a map upfront, and then operators can delve into the specific substations,” Joseph says. “Before, we had to install software to view the network on a different computer, and that was a big deployment issue as we wanted anyone to see it.”
Transmission monitoring is now available to any National Grid UK personnel with an Internet connection, and provides both real-time and historical data. “If there’s an event on the network, we can now demonstrate the event at different places throughout the network in playback mode,” Joseph says. “If we don’t know where the phase unbalance has originated from, we can probably pinpoint where it has originated from by looking at the recordings from the different substation monitors.”
“We designed our own apps basically and wanted it a certain way, not what others thought we might want,” Joseph says.
National Grid UK is still deploying all the monitoring substations, but initial rollout has been successful with the mobile substations. “I can’t really overemphasize the value of having something that we can reprogram, since all the physical connectivity is pretty much sustained,” Joseph says.