Using a handheld infrared imager, Keith Weyh, technical services supervisor at Adams Columbia Electric Cooperative, monitors the health of the co-op's equipment, the equipment of its members, and sometimes even the equipment of the transmission company supplying its substations.
The Adams Columbia Electric Cooperative (ACEC) serves about 35,000 members in 12 mostly rural counties in central Wisconsin. Of course, many members are dairy farmers, but the cooperative also
serves about 13,000 seasonal residences, 600 irrigation services, approximately 1,500 small commercial accounts, and nine large facilities, including a chicken processing plant, an ethanol plant and a federal prison. To service these members, ACEC has 28 substations, more than 5,000 miles of power lines (about 2,700 miles underground and approximately 2,400 miles overhead) and the related equipment.
Until early in 2004, ACEC contracted with Wisconsin Public Service Corporation (WPSC) to do the co-op's thermography (or thermal imaging). Annually, a WPSC technician used a thermal imager – also called an infrared (IR) camera – to make two-dimensional representations of the surface temperatures of equipment in the co-op's substations. What those images sometimes revealed were hot spots on the equipment, which typically means a component is likely on its way to failure and should be serviced.
If an inspection uncovered what appeared to be a critical problem, a supervisor was called to request that a line crew make repairs. There was no provision for follow-up imaging to determine if effective repairs were made. In one case, it was two years between the detection of a failing regulator and confirmation that it had been repaired.
Justifying a camera purchase
Clearly, the outsourced, once-a-year inspections were not getting the job done. That fact – and several other factors – led to the decision to bring thermography in house.
One important issue was the need to protect expensive equipment. A substation transformer costs about $200,000. A 2000 kVA commercial transformer costs $19,000, and a regulator costs $15,000. The co-op has more than 100 regulators in its system. Keeping just one of them from being destroyed would nearly pay for the imager ACEC was considering.
Another factor influencing the decision to stop outsourcing thermal imaging was the desire to reduce overtime work caused by outages. In a single year, the co-op spent nearly $900,000 after hours to deal with outages. That figure included labor, benefits and transportation, but did not include the cost of materials or costs for outages handled during normal working hours. The imager the co-op was considering could be purchased for only two percent of after-hours overtime costs, so it easily would pay for itself in outages prevented.
Given these considerations, ACEC management set about securing an IR camera for the organization with the understanding that Keith Weyh would do most of the thermography. Weyh, a long-time lineman and the co-op's current technical services supervisor, assisted in the selection process. Early in 2004, the utility purchased its own thermal imager: a Fluke Ti40. Weyh says he preferred the camera based on ergonomics and ease of use.
Thermal imaging at ACEC
With no formal training, Weyh was able to begin using the new camera right away. He attributes his ability to do that to his years of experience in the electric utility service sector, his experience using a handheld, non-contact IR thermometer and on personal research. Weyh says that training might be helpful, but what he looks for with the IR camera is pretty simple. One just needs to understand emissivity; or in other words, understand that not all energy emanating from an object is emitted by the object -- and then know what to do in situations where reflected heat may be affecting an IR image.
Today, Weyh, armed with this knowledge and his thermal imager, inspects the co-op's equipment, the equipment of members and sometimes even the equipment of the transmission company supplying power to ACEC's substations. Here, in part, is what he inspects and how:
As he scans the rest of the substation, he specifically follows the circuit as it comes from the transmission line. He scans the fuses and contacts on another gang-switch within the station. He scans the high-side insulators (arrestors) and the high-side bushings on the transformer. "Right now," he says, "I am monitoring a bushing in one substation that is running about 40 °F higher than similar bushings under the same conditions. We're keeping a close eye on that situation and trying to figure out when we can plan an outage and take care of the problem."
Next, Weyh inspects the substation's bus work, which has bypass switches that sometimes cause problems. At one substation, the technical services team used a visible-light digital camera in addition to the thermal imager to find the root cause of a problem with a bypass switch. A visible-light image revealed that the bus work did not have any allowance in it for contracting during the cold winter months. So, at that time of year, the bus work distorts the problematic bypass switch, causing the problem. "Again, it's something we will schedule and take care of," Weyh says.
Finally, the team leader uses the infrared imager to scan the regulators, the low voltage-bus and the recloser for each circuit that goes out of the substation.
Every quarter, Weyh performs inspections like that just described on every ACEC substation.
On underground lines, there are cabinets every quarter of a mile to give service personnel access to elbows (connecting devices). Weyh opens each cabinet and performs a physical and infrared check for overheating. "In the past," he says, "we've had elbows burn up and destroy cabinets. Then, service personnel had to cut up and splice the cable. Now, with the IR camera, we can go out and look for overheating connections and replace them before they fail and destroy cabinets."
Also, on the longest three-phase lines are the 35 regulators mentioned earlier. These get inspected twice a year along with the associated MOV arrestors and bypass switches.
Key accounts. Weyh considers seven of the co-op's members to be key accounts. These he inspects twice a year, scanning all of the ACEC-owned facilities on each site. The largest, the chicken processing plant, has a complete substation dedicated to it, and it has dozens of the utility's transformers on site – eleven 2000 kVA units plus numerous other small ones.
"It pays to go through there a couple of times a year and check all of the elbow connections," Weyh says. He explains that every transformer has an elbow connection for an underground cable. Also, there are switches on the system to be checked. They support loop feeds that offer alternatives designed to keep the plant operating when electrical service work is required.
"There is a lot of investment in that facility," Weyh notes. "If we can head off damage, we have done our job." For example, a couple of years ago, when he was going through the plant with the IR camera, he found overheating where an elbow plugs into a bushing well that's screwed onto a stud bolt on a transformer. As a result, the utility scheduled an outage for the weekend. Sure enough, the stud was nearly twisted off. It was replaced, but Weyh conjectures that had it failed under load, it probably would have destroyed the transformer.
To underscore the fact that most utility problems are easy to spot, Weyh reports on the inspection of one farm pole where he used the infrared camera to determine there was a problem even though the actual temperature of the pole top was outside the calibrated range of the instrument. He notified the co-op member, who contacted an electrician and scheduled repairs for the following week. Unfortunately, the pole top burned before repairs could be made.
Problems and pitfalls
Asked what on-the-job problems he encounters while doing thermography at ACEC, Weyh mentions the following:
Asked to sum up his experience with a thermal imager, Weyh says, "It has been a good tool. My thoughts are that eventually we are going to catch up, and I'm not going to be finding as many problems." Then he laughingly adds, "Hopefully, I'll work myself out of a job," but quickly notes, "No, the camera will always have a use here."