This is Part 2 of a two-part series. Part 1 of the series was published Feb. 3.
Smarter grid, more secure grid
In addition to synchrophasors and other devices intended to make the transmission system smarter, other developments are aimed at enhancing the security of the high-voltage system. One of those is the transmission line security monitor (TLSM), a hotdog-shaped, football-sized device developed and licensed by Idaho National Laboratories (INL).
In the wake of 9/11, with security concerns at the fore, INL was charged with developing a way to protect high-voltage transmission lines from acts of sabotage.
The limitations INL researchers faced were daunting.Of particular interest and concern were the numerous lines that cross remote areas where there is no infrastructure in place to protect them – no power source other than the transmission lines, no cell phone service for communication, and often the only access available along primitive access roads.
To overcome these limitations, INL developed the first TLSMs – devices that would be mounted to the transmission wires and draw power directly from the conductors. With one TLSM per tower – approximately one every quarter-mile – low-power RF links with a range of several miles would enable the devices to transmit the information from one TLSM to the next, and to leap-frog over several towers if necessary, until the data reached the control room.
Early TLSMs were designed to monitor factors that, history had shown, were the greatest indicators of security risk to power structures.
“The nodes, one on each tower, look at the base of the tower with an infrared sensor and try to detect warm-body motion,” John Svboda, lead investigator with INL on the TLSM program told TransmissionHub. “At the same time, they’re also looking for abnormal vibrations that are not due to natural occurrences.”
Utilities’ experiences in other countries had shown that such vibrations could be due to perpetrators trying to remove bolts at the base of the tower “and letting Mother Nature take the tower down at a later date, in a high wind or a storm,” Svoboda said.
Simple analysis of the collected information would indicate whether events were innocuous – an isolated incident of a deer or a hiker passing by one tower, for example – or bore further investigation.
“If you get both alarms – the movement of a warm body and abnormal vibration – and if those events move to adjacent towers, then you’d get very nervous and likely alert local authorities or get someone out there immediately to figure out whether someone has been tampering with the power,” Svoboda said.
When utilities evaluated the devices, Svoboda said their response was positive but that “what we really want is operational information on those transmission lines.” INL therefore joined forces with Lindsey Manufacturing Company, a 65-year-old Azuza, Calif., company that manufactures high-voltage transmission equipment, sensors and hardware, to develop technologies that could be used to aid the utility in operating the line.
“We added ways to measure line sag, conductor temperature, tilt and angle of the conductors, and measurement of the distance to [anything beneath the line],” Svoboda said. “We added several different kinds of sensors that would allow the operators to get added value from installing the security monitors on their transmission lines.”
“We have two sets of vibration sensors [which are] very important because, if the conductor is not vibrating, we know there’s no wind,” Phil Spillane, VP of marketing and sales for Lindsey Manufacturing told TransmissionHub. “These sensors sense Aeolian vibration, which is wind blowing across the conductor, and in the wintertime when we have heavy ice, we have the galloping effect of the conductor.”
In addition, features in the TLSM will enable utilities to maximize the capacity of lines by utilizing forecasts to calculate the line’s dynamic capacity. “By gathering weather history from a location of an installed TLSM, line current history, and exact conductor height history, we can forecast 24 hours in advance how much additional transmission line capacity is available without violating clearance regulation,” Spillane said.
Developers say the devices are easily deployed. “They’re live-line installable with hotstick, or by a live-line crew,” Spillane said. They can also be installed by direct connect when the power is down, thus giving utilities a great deal of flexibility in deciding when, where, and how to install the TLSMs.
(The photo at right shows a hotstick crew completing the installation of a TLSM. The TLSM is the small node on the line directly above the crew.)
An important consideration is cost. While a final per-unit price has not been set, Spillane said their cost will be about half that of existing devices and technology, “none of which comes close to the functionality of the TLSM,” Spillane said.
Lindsey Manufacturing is fine-tuning the design and functionality of the TLSM and intends to introduce it to utilities at the IEEE/PES Transmission and Distribution Conference in Orlando, Fla., in May.
Spillane said the devices could pay for themselves many times over, “by protecting the power lines themselves but more to the point, the millions of dollars of energy that flow through them every day.”