Best Practices, Power Quality Matters
The Hidden Flaw of Aerial Bundle Conductors
The Hidden Flaw of Aerial Bundle Conductors (ABC)
What textbook engineering fails to teach you about harmonics and nuisance tripping.
The account I am about to share will likely be disputed by “younger electrical engineers”—those who have degrees but lack decades of grueling, hands-on field experience. But veteran field workers know the truth: Aerial Bundle Conductors (ABC) cause severe harmonics.
The Wilderness Case Study
In the early 1980s, during my tenure with a major power utility, a brand new 11kV ABC line was constructed in the Wilderness area. The high-profile project was fast-tracked specifically to supply power to the private residence of a former prime minister.
The line, however, was a disaster. It remained operational for only a short period due to persistent, unexplained “nuisance tripping.” At the time, our team couldn’t pinpoint the exact cause. It was only much later that advanced diagnostic tools revealed the protection systems were reacting to severe current and voltage distortions caused by internal harmonics. Ultimately, that expensive ABC line had to be scrapped and replaced with a standard bare-conductor overhead power line.
The Secret Anatomy of an ABC Failure
Despite early warning signs, the industry continued installing these cables for years. It wasn’t until thorough investigations were launched into widespread, spurious tripping that the exact destructive mechanism was uncovered:
The Ghost in the Grid
This degradation creates a frustrating failure cycle that drives grid operators mad: The line trips, recloses (restores power), vaporizes the immediate moisture, and stays connected stably for a while… until the moisture creeps back in and repeats the cycle.
Following these definitive findings, the utility quietly decided that 11kV ABC cables would no longer be installed. While Low Voltage (LV) ABC cables undergo the exact same scenario, it occurs on a far lesser, less destructive scale due to the lower voltage stresses involved.
