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Mysterious tranmission falures investigated by technology, staff

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​by Lisa Meiman

Two Rocky Mountain transmission lines in Wyoming are sporting new hardware in a first-of-its-kind sensor demonstration to investigate why the lines are experiencing uncommon failures.

Nineteen sensors and two base stations from the Electric Power Research Institute were installed on the Ault-to-Hayden 345-kilovolt and Miracle Mile-to-Snowy Range 230-kV lines, Nov. 12-13, to measure equipment movement, vibration and weather conditions that could help identify the cause of the mysterious failures.

“We’re experiencing damaged structures in Wyoming with unknown failure modes,” said Headquarters Electrical Engineer Bill Timmons. “We think it might be due to galloping lines or other wind-related causes. The sensors will help pinpoint what’s going on.”

RM Foreman III Lineman Ed Hunt shared the specific issues: “On the 345-kV line, we are experiencing spacer damper failures. Once the damper fails, the subconductors may start banging together. Sensors were placed on two spans of this line: one with the old dampers and the other with new dampers. We will be checking for differences in performance.” The Ault-to-Hayden line is a trust project, meaning Western maintains it on behalf of a paying customer, so RM also needs data from the sensors to justify funding a project to replace the dampers.

The 230-kV line is only four years old, but is already falling apart along its path between Cheyenne and Laramie, Wyoming. “Hardware is wearing out and dropping the static overhead ground wire and fiber. We have replaced four or five dropped statics and a lot of hardware that holds the static in place,” said Hunt. Crews have been called out to replace snapped H-frame structures believed to be caused by extreme wind shear, or where wind speeds are different at different altitudes. Crews are using the sensors to test both the current set up and a new configuration of the line to identify the problem and see if the different configuration performs better.

The Cheyenne line crew installed nine sensors on the 345-kV line with 10 placed on the 230-kV line. One base station was installed on each line to relay movement and weather data to an EPRI server. HQ Electrical Engineer Josh Ross will analyze the data via Web portal for a year to identify trends and relationships between weather conditions and equipment movement.

Galloping lines run with wind 

The wind also made a showing. “It was so cold and pretty windy. When the 170-foot boom on the bucket truck was fully extended, it swayed about four feet,” said Ross. 

The main suspect for both problems is Wyoming’s famous wind. Average annual wind speeds in Wyoming are about 13 mph with 3-second wind gusts over 60 mph, according to the National Weather Service. Gusts and ice are often the culprit for galloping conductors, while sustained wind speeds and quick temperature changes are responsible for Aeolian vibrations that, over time, literally shake equipment to pieces. Both galloping and Aeolian vibrations, along with higher-than-average wind speeds, are believed to be at play for the two lines.

The EPRI sensors measure conductor or static temperature, current, movement along every axis and the speed of the motion. Two sensors placed on 230-kV H-frame structures will measure vibrations and movement of the structure.

The base stations measure weather conditions including temperature, humidity, wind speed and wind direction, adding environmental data to movement information. The base station then relays all the data to the EPRI-hosted Web portal.

“EPRI is a leader in power sensor technology, and their sensors are the best way we know to analyze vibration and movement. The sensors are also lightweight, and the conductor sensors harvest their own power,” said Timmons.

There are also considerable future possibilities for sensor technology to support asset management and reliability-centered maintenance. “If the sensors come back with useful data, these sensors could be deployed Westernwide to identify other anomalies,” added Hunt.

Cheyenne crew members, from left to right, Foreman II Lineman Ron Miller and Linemen Taylor Pauley and Jeremy Watson install a base station on a lattice steel structure, Nov. 12. Using data gathered from this station and almost 20 sensors, maintenance crews and engineers hope to discover why two lines in Wyoming are failing and if different configurations may prevent more damage. (Photo by Ed Hunt) See more photos at our Flickr collection.

​What polar vortex? 

Wyoming’s weather did not disappoint during the install in mid-November. At the time, the Rocky Mountain states were in the throes of the season’s first polar vortex. “On the first day, the wind chill was below zero and the high was about five degrees. On the second day, the high was about 11 degrees,” said Hunt. “We had a short window to install the sensors. The EPRI folks needed to be out here to help with the install; they are from North Carolina so scheduling was an issue. We had to do it now or wait until spring and miss the data the winter would have provided.”

Page Last Updated: 7/14/2015 6:56 AM