Distributed Sensing on a 110-kV Overhead-Line Maintenance Operation on an Operational Optical Ground Wire

Introduction

• OPGW combines a lightning-shield conductor with embedded communications fibers, and DAS and DTSS can measure dynamic vibration and quasi-static strain along the cable.Operators otherwise relied solely on crew reports to confirm maintenance completion.Source: Introduction · p. 1
• Prior OPGW and adjacent-fiber DAS studies focused on passive events such as wind, ice loading, faults, intrusions, or electrical discharges.Earlier work also demonstrated vibration reconstruction, ice detection, sag extraction, and mechanical-intrusion classification.Source: Introduction · p. 1
• The study reports combined DAS and DTSS measurements of a controlled cable lift, resolving its mechanical sequence and detecting localized residual strain at the re-clamped tower.The sequence includes ground contact, crane lift, and re-attachment.Source: Introduction · p. 1

Experimental Setup

• The embedded fiber spanned 33.9 km with ∼8 dB link loss; the monitored line included the maintenance tower near 360 m and a tension tower at 3360 m.A 1650 nm OTDR trace with 100 ns pulses confirmed the link length; the interrogator shared the fiber through a 1550/1650 nm filter.Source: Experimental Setup · p. 2
• DAS used 100 ns pulses and a 10 m gauge length, sampled at 250 MS/s with ∼0.4 m sample spacing and an 800 Hz pulse repetition frequency.A 15–350 Hz bandpass filter was applied during the three-hour measurement.Source: Experimental Setup · p. 2
• DTSS was acquired after maintenance at approximately 10 m spatial resolution, using a 10.6–11.0 GHz local-oscillator sweep and 2 MHz frequency resolution.Without a pre-maintenance reference, relative BFS variations were interpreted as localized strain, although differential temperature between spans could not be fully excluded.Source: Experimental Setup · p. 2
• During planned maintenance, the line was de-energized, isolated, and grounded, and all conductors, including the OPGW, were lowered to the ground.DAS began while the cables rested on the ground and continued through the crane lift, re-attachment, and post-maintenance period.Source: Experimental Setup · p. 2

Results

• Before lifting, the ground-resting span showed ∼3 nϵ dynamic strain; freely suspended aerial sections showed 22–44 nϵ.The 320–740 m low-variation corridor contracted after lift, with only ∼320–390 m remaining at ∼3 nϵ.Source: Results · pp. 2–3, Figure 2 · p. 2
• Dynamic-strain features extended from ∼390 m to the tension tower at 3360 m, where the dead-end clamp blocked further propagation.A similar reduction appeared near another tower at ∼3100 m; the underlying coupling mechanism remains subject to further investigation.Source: Results · pp. 2–3
• Two chain-collision events matched on-site audio and DAS reconstructions, with cross-correlations of ρ = 0.79 and 0.71.Both filtered waveforms had a sharp onset and oscillatory decay at a comparable dominant frequency of ∼65 Hz.Source: Results · p. 3, Figure 3 · p. 3
• Up to ∼398 µϵ of localized residual strain appeared between 100 and 436 m after maintenance, while the aerial link to Virtsu remained near 0 µϵ.The affected region extends beyond the maintained span toward Lihula, consistent with tension redistribution between adjacent spans.Source: Figure 4 · p. 3, Results · p. 3

• Up to ∼398 µϵ of localized residual strain change over a ∼336 m section at the re-clamped tower indicated an altered static tension distribution.Source: Conclusion · p. 3
• DAS recorded dynamic strain from ∼3 nϵ with the cable on the ground to ∼22-44 nϵ when freely suspended between spans.Source: Conclusion · p. 3
• Phone-recorded chain collisions matched DAS events, indicating potential for DAS playback as a classification tool.Source: Conclusion · p. 3
• The measurements demonstrate OPGW’s potential as a real-time asset monitoring tool for grid operators using DAS and DTSS.Source: Conclusion · p. 3