- Buyer's Guide
On a day last month, in the early morning hours, I embarked on the scheduled task of inspecting the miles of power lines that are strung throughout the chemical plant in Central Florida where I work as a reliability analyst. The task was simple. I was to perform an infrared and ultrasound inspection on the high-voltage power line connections, disconnects, fuses and transformers, as well as the electrical equipment and components, located in nine substations throughout the facility.
I started on the southeast side of the plant and worked my way northwest toward the two steam turbine generators that were supplying several plants as well as the public power grid with an approximate combined load of 59 megawatts (MW) at 69 kilovolts (KV) that morning. I found several small problems working my way around, including a few high-voltage components with corona activity present that I observed and recorded with the ultrasound equipment as well as a faulty connection at a fuse clip on a high-voltage line supplying power to a processing plant that I observed and captured with an infrared camera.
Then I saw something strange with my own eyes. Just two power poles away from the first turbine was a bright red line above my head. At approximately 5:30 a.m., I found myself in the dark, spinning in a circle, looking up, down and all around, visually trying to figure out where the reflection was coming from. Then it hit me! It wasn’t a reflection. I could visually see the 69 KV power line glowing bright red in the dark. Stepping back away from the pole, I viewed it on the IR camera from what I felt was a relatively safe distance and angle, just in case the line decided to break and fall in my presence.
PdM analyst uncovers issues on 69 KV power line
On the center phase jumper, I observed a pretty apparent inaccurate temperature of approximately 312 degrees Fahrenheit. That reading was due to being out of my measurable field of view with a Delta T of 228°F and another anomaly that was not seen visually with an inaccurate temperature of approximately 137°F with a Delta T of 57°F on the lower phase. Undeterred by the inaccurate measurements, I still saved the image. At the time, I believed that the temperature of the center phase jumper must have been at least 800°F in order for it to produce the bright red glow that was visually present. I also snapped a visual picture in an attempt to capture an image of the line glowing in the dark. I immediately informed the production manager in charge of the turbines and escorted him to the pole so he could see for himself that it was glowing. After his visual conformation, he informed his superiors immediately of the situation at hand.
Within a few hours of discovering the fault, plant reliability engineers, maintenance planners and the plant electrical superintendent had a plan in place to perform an unscheduled power outage and repair the connections immediately in an effort to avoid the additional cost that would be incurred if the plants were to shut down abruptly without any notice at all.
The power line that was isolated was leaving one of the steam-driven turbines carrying a load of approximately 34 MW at 69 KV when the fault was discovered. It supplied power to the local power company’s grid as well as six different processing plants, administrative offices and one maintenance shop. All of them were shut down unscheduled but were given enough notice to reduce any additional cost of corrective measures that would have needed to take place had the plants gone down without the proper procedures and protocols being followed.
Upon shutdown, the high-voltage electricians discovered the connections on the jumper that had been glowing were so damaged that the entire line length had to be replaced from one pole to the other. The initial investigation indicated an improper compression connecter was used to splice the jumper to the line going to the next pole. The connector was sized for the gauge of wire used between the two poles; however, the jumper was of a smaller gauge, thus making a weak connection. This was headed for catastrophic failure.
The faults were reassessed the following morning after the proper corrective measures were taken. The Delta T on both faults was reduced to within 5°F under approximately the same load, ambient and surrounding conditions.