The fault was caused by voids in the cement, the report said, however these were not known at the time, despite the insulators having been used since the 1950s.
The coroner said a double insulator failure had “not been known to previously occur”, with witnesses called to give evidence at the inquest referring to it as “not experienced before”, “complex” and “very unique”.
An investigation by ENWL, which provides electricity in the county, found the voids were “introduced during the manufacturing process”.
Gomersal’s report said ENWL had not known about the low-hanging line until after the incident.
“Evidence was consistent that, at the time, there was no automated mechanism to detect a low-hanging line and that [the] electricity industry relied on low-hanging lines being reported by members of the public,” she said.
In light of the death, ENWL brought in a number of measures to avoid similar incidents.
Gomersal said ENWL told her it had stopped using porcelain insulators and was rolling out a programme to replace them at about 8,000 locations.
Where there is a fault similar to the one that had occurred leading up to the 29-year-old’s death, ENWL now carries out patrols of lines within 48 hours.
It has also developed a technology called Linesight, which can detect low-hanging lines and issues with insulators.