Ameren Illinois Enhances Power Line Reliability with Advanced Inspection Technology

More than 45,000 miles of sub-transmission and distribution power lines span the Ameren Illinois service territory, and about 1.3 million utility poles, including 2,000 high-strength composite poles, support this infrastructure. To boost reliability and minimize outages for customers, field crews are inspecting, upgrading, replacing and rebuilding sections of line.

“A utility can continue replacing poles in poor condition, but at some point, the conductor itself must be upgraded—either through reconductoring or a full line rebuild using modern designs,” says Randy Thoroman, director of Strategic Initiatives for Ameren Illinois. “This approach not only strengthens both the overall line with more modern conductors and structures for improved reliability and resiliency but also enables higher capacity to support future load growth, economic development, and the state of Illinois’ Climate & Equitable Jobs Act goals, which is moves Illinois to 100 percent carbon-free power by 2045.

Sub-transmission lines can last for 60 to 100 years, depending on loading conditions. Over time, however, weather conditions can cause the steel core of a conductor to rust and pit. This deterioration can reduce the rated tensile strength (RTS) of the steel core, leading to possible conductor failure and less reliability and safety.

Traditionally, engineers and lineworkers have been able to determine which lines had the most deteriorated conductor in Ameren Illinois’ service territory. The utility, however, has 100-plus aging lines that are nearly 80 to 100 years old, leaving it with the question: how do you identify and prioritize replacements of those lines based on the most deteriorated conductor?  

Ameren’s field workforce conducts periodic inspections of poles and equipment, and this work practice continues in support of evaluations of line rebuilds. Conductors, which are considered critical assets on the poles, were only visually inspected primarily. When data warranted, they would also perform an engineering analysis by removing a short section of sub-transmission conductor and sending it to the lab for evaluation. While this method gave the utility deeper information about the conductor, it was also manually intensive, said Kyle Maxwell, superintendent of Electric Operations for Ameren Illinois.

“We found that the old method does not provide a complete view of the entire conductor span, only the short piece that is submitted to the lab,” Maxwell said. “It is hit or miss if that is the most representative section for the entire span.”

Identifying the Condition of Conductors

Recently, Ameren Illinois embraced a new approach to line inspection and maintenance by leasing a Kinectrics LineVue device, which provides a complete analysis of the length of the conductor span.

“It is a more accurate estimate of the health of the entire conductor,” said Riley Adams, senior manager of Electric Programs for Ameren Illinois.  “The Kinectrics LineVue device enables us to identify the remaining RTS of the steel core and prioritize which aged sub-transmission lines that are at end of life that need rebuild first. This approach focuses available funding to the highest priority projects.”

Using the technology, Ameren Illinois can more quickly and accurately determine when sub-transmission power lines should be upgraded. The device can assess the steel core of wires, whether they are aluminum steel reinforced or aluminum core steel supported, to identify any potential defects such as pitting, rusting and loss of steel core strength, or broken strands in the line, to determine when they should be replaced.

Patrick Smith, senior vice president of operations and technical services for Ameren Illinois, said data from LineVue will aid decisions on which circuits to upgrade under the company's Multi-Year Integrated Grid Plan. Traditionally, Ameren Illinois has not been able to perform inspections for conductors on sub-transmission power lines due to the high cost and feasibility. The LineVue device is not only able to perform this inspection in a more cost-effective manner, but it is more accurate as well, he said.

"Our customers count on us to invest prudently in infrastructure to improve the performance of our energy delivery system," Smith said. "Technology like LineVue is part of our overall plan to install a smarter, more modern energy grid to reduce outages and improve energy affordability."

Remotely Controlling the Device on the Line

So far, Ameren Illinois has 14 LineVue certified internal operators, consisting primarily of field-based electrical engineers. Kinectrics provided an on-site three-day course for the utility’s region-based engineers who are now certified operators.

Ameren Illinois trainers can also provide a one-day refresher course for operators who do not use the device daily since it is often passed from team to team. Before an engineering team of two uses the device, the utility also provides a one-day refresher training course using a short test span of conductor before use.

To use the technology, a certified operator must first place the remote-controlled, motorized, battery-powered device on the conductor on a sub-transmission line. As the device crawls along the conductor, LineVue measures the remaining cross-sectional area of steel core wires, detecting local breaks and corrosion pits. It can be used on energized lines up to 500kV as well as de-energized lines.

As the LineVue certified operator controls the device and the computer, the motorized device proceeds along the conductor inspecting about 100 ft per minute in both the forward and reverse directions. It transmits the inspection information to a computer linked to a ground station that transmits and receives inspection results. An Ameren Illinois operator then logs the results, and the data is sent to Kinectrics for evaluation by LineVue engineers. They then provide a report for each span tested that identifies the remaining RTS of the conductor steel core.

Ameren Illinois tests about 2% of the conductor spans on a sub-transmission line or about 30 to 40 spans to obtain a good picture of the health of the conductor. The engineering team compares the average test results in percentage of RTS and the worst test results of each line tested to identify the priority of sub-transmission line replacements.

For example, when looking at a sub-transmission line with test results of 51% of RTS compared to a different line at 75% of RTS, the lower RTS would be a higher priority based on conductor test results. The engineers also factor in other signs of deterioration on the line such as number of splices to identify the priority of line replacements.  In addition, other factors such as overall pole health of circuit, pole hardware, loading and location are also taken into consideration.

The technology has helped both lineworkers and engineers to evaluate the condition of conductors and determine what needs to be replaced.

“The LineVue inspection results have shown that aged aluminum conductor steel-reinforced conductors with a steel core remaining RTS below 85% of original RTS to be problematic and conducive to failure,” Adams said.

Rolling Out the Technology

Ameren Illinois compared LineVue test results with cutting out a short section of conductor on the same LineVue tested span. The review found that the LineVue device evaluates the condition of the entire conductor span, pinpoints the lowest reduced RTS and delivers an accurate assessment of the overall conductor health.

“The older method used to evaluate a short piece of conductor is accurate for the short conductor section but is it hit or miss if that short section is the lowest RTS represented in the span,” Adams said. “LineVue is able to evaluate more of the conductor to be more representative of the circuit overall.”

Ameren Illinois discovered that the LineVue device and inspection results are an accurate and low-cost method to inspect and provide data in support of investment decisions.

“Without accurate data, a utility may be replacing a line based on local knowledge that may be accurate but may not be the highest priority for reliability and safety as compared to other lines on the system,” Adams said. “LineVue provides a more accurate data for our engineers, ensuring we are doing the right work at the right time, and provides the data needed to stakeholders such as our regulators.”

 In the beginning, Ameren Illinois borrowed a device from a California utility, and it was operated by Kinectrics operators. The utility deployed the technology as part of a pilot program to inspect sub-transmission power lines in Joppa, Galesburg, Washington and Easton, Illinois. Since the initial testing, the company leased the device for three years.

“Our plan is to test about 150-plus lines that are on the aged line list,” Maxwell said.  “Our crews support using the device as compared to cutting out 40 short sections to identify the condition of the conductor.”

By taking a proactive approach to line inspections and maintenance, Ameren Illinois can increase the safety and productivity of its field workforce. At the same time, the utility can adhere to the pillars of its grid modernization plan by prioritizing asset replacement and ramping up reliability.