How Traveling Wave Innovation Solved 8 Years of Unexplained Faults

When 20,000 Consumers Depend on a Circuit Nobody Can Diagnose—And Helicopters Can't Find What's Causing Repeated Trips

For eight years, Scottish and Southern Energy faced an escalating crisis on a critical 132KV teed circuit serving 20,000 consumers. Starting in 2006, fault trips increased annually with no identifiable cause. Helicopter patrols at £6,000 per day scoured remote, wooded terrain. Foot patrols searched miles of towers across hills, valleys, and a loch crossing. Nothing was found. The faults kept occurring—mostly between 4 am-6 am during the summer months, primarily on the top phase.

The Fault Location Problem: Traditional Methods Couldn't Solve

Impedance-based distance relays were useless on the teed configuration. Even traveling wave systems using standard current sensors failed because the tee terminated on high-impedance transformers, causing all faults to appear at the tee junction instead of their actual location, leaving a 19km search area through inaccessible terrain.

What You'll Discover:

Eight Years of Forensic Fault Analysis – Review detailed investigation of 85 line trips, analyzing fault distribution by time of year, time of day, and phase involvement—revealing patterns that pointed toward suspected bird interference from a nearby landfill opened in 2006.

The Voltage Sensor Breakthrough – Learn how SSE solved the impossible tee location problem by installing couplers on transformer bushing test taps to measure voltage transients instead of current, finally enabling accurate three-ended traveling wave fault location.

Comprehensive Remedial Strategy – Explore the multi-million pound program: University of Manchester insulator assessment, complete insulator replacement with longer creepage paths, earth wire renewal, bird deflector installation on 7 towers, and structural surveys dating to the 1950s construction.

Proven Results – See how the first fault after commissioning pinpointed the location to within 1km of Dunoon, narrowing search areas from 19km to just 1-2 towers and dramatically reducing investigation costs.

Download this case study to learn how innovative sensor placement solved an eight-year mystery.