Power Cable Fire Detection & Temperature Monitoring
DTS full-line temperature monitoring + DAS underground gallery intrusion warning — two defenses on one fiber base.
What is distributed fiber optic monitoring for power cables?
Distributed fiber optic monitoring for power cables uses DTS (Distributed Temperature Sensing) and DAS (Distributed Acoustic Sensing) on a single fiber base to protect underground cable corridors. The DTS fiber is laid continuously along trunk lines, cable trays, manholes and joints, reading a temperature value roughly every meter — ±0.5 °C accuracy with 0.8 m spatial resolution — so an overheating joint is caught during its gradual rise, not after ignition. At the same time, DAS listens along underground galleries for intrusion and third-party construction with meter-level localization. The result is two defenses on one continuous, EMI-immune sensing line with no electronics installed along the cable itself.
Four pain points of urban cable safety — from overheating joints to third-party excavation
Joints & manholes overheat
Cable joints, terminations and manholes are overheating hotspots — scattered and numerous, hard to cover with point sensors, and fires brew silently.
Fire = loss already
Overload and aging cause a gradual temperature rise; smoke detectors only alarm after ignition, missing the best response window.
Underground gallery intrusion
Underground power galleries face illegal intrusion and third-party construction threats — any cable damage causes wide-area blackouts.
Manual patrol is inefficient
Manholes and galleries are scattered and harsh; patrol cycles are long with many blind spots, and continuous watch is impossible.
Architecture: temperature + intrusion dual defense
Two sensing layers share one fiber base — fire prevention and intrusion warning in a single platform.
DTS full-line fire early warning
DTS is laid continuously along urban trunk lines, distribution channels, manholes and joints, delivering ±0.5 °C accuracy, 0.1 °C resolution, 0.8 m spatial resolution and 50 °C/min response sensitivity — one temperature point per meter, alarming and localizing temperature rise before a fire starts.
DAS gallery intrusion warning
DAS monitors vibration and acoustic signatures along underground power galleries in real time, identifying illegal intrusion and third-party construction with meter-level localization — sharing one host and fiber base with cable temperature monitoring.
Installation without an outage: how a typical deployment works
From corridor survey to dual-defense operation — with the live cable untouched.
- Step 1 — Survey the corridors. Record cable routes, manhole and joint positions, gallery access, and available fiber or duct resources.
- Step 2 — Design the two defenses. Plan DTS channels — 30 km per single-mode channel, 20 km per multi-mode channel — and add DAS where underground galleries need intrusion coverage; both layers share one host platform.
- Step 3 — Install without an outage. The sensing cable is laid along cable trays without electrical connection to the live cable; the exact process is confirmed after a site survey.
- Step 4 — Commission the baselines. Set per-section temperature thresholds and rise-rate alarms (50 °C/min response sensitivity), and calibrate DAS event patterns for the specific gallery.
- Step 5 — Operate and integrate. 24/7 monitoring with 0.8 m localization feeds alarms into the existing control room, with temperature trends archived for asset management.
Core capability metrics: accuracy and overheating response
Why DTS beats point temperature sensing
Distributed fiber sensing covers the whole line continuously at 0.8 m resolution — no blind zones, no power, no networking, immune to EMI — with far lower lifecycle cost than a point-sensor scheme. View the DTS product
Conventional point sensors vs distributed fiber monitoring
A factual comparison of common approaches for cable temperature and gallery safety.
| Dimension | Traditional point-based sensors | Periodic manual patrol | Distributed fiber monitoring |
|---|---|---|---|
| Coverage | Spot coverage at chosen locations; joints and manholes are numerous | Cycles leave long unwatched windows | One temperature point per meter along the full line, 0.8 m resolution |
| Detection timing | Typically reacts once heat has spread to a sensor | Often after visible smoke or damage | During the gradual temperature rise — typically days to weeks before smoke detectors |
| Localization | Only at the sensor position | Found on the next visit | 0.8 m spatial resolution with ±0.5 °C accuracy |
| In-service operation | Each point needs power and networking; electronics age in manholes | Labor-intensive; confined-space exposure | Passive fiber laid along trays, no electrical connection to the live cable |
| Interference immunity | Electromagnetic interference near power cables is a constant risk | Human judgment varies by crew | Optical sensing, immune to EMI, stable near high-current cables |
Operations: alarm thresholds, trending and maintenance practice
What running the dual-defense loop involves after commissioning.
Once commissioned, the system runs as a standing early-warning layer, and the operating workload concentrates on a few well-defined routines:
- Threshold stewardship. Per-section temperature thresholds and rise-rate alarms (50 °C/min response sensitivity) are reviewed after load changes, re-tiling or seasonal extremes, so alarms stay meaningful as the corridor evolves.
- Hotspot trending. Every joint and manhole accumulates a temperature history; a location whose baseline drifts upward across months becomes a planned-maintenance candidate long before it breaches an alarm level.
- Intrusion workflow. DAS gallery events arrive with meter-level localization and a classification; the control-room response is a targeted dispatch — not a gallery-wide search.
- Integration upkeep. Alarm feeds into the existing control room are re-verified after any SCADA or NMS upgrade, keeping the monitoring layer a peer of the electrical protection layer rather than an afterthought.
The practical outcome: overheating joints are found during their gradual rise — typically days to weeks before smoke detectors would react — and third-party excavation near galleries is intercepted before a cable is struck.
Key terms
- DTS (Distributed Temperature Sensing) — continuous temperature profiling along the cable route, one reading per meter.
- DAS (Distributed Acoustic Sensing) — vibration and acoustic monitoring along the same fiber base, used for gallery intrusion and third-party construction warning.
- Spatial resolution (0.8 m) — the granularity at which a temperature reading is assigned to a position along the route.
- Rate-of-rise alarm (50 °C/min) — an alarm rule triggered by how fast temperature climbs, not only by its absolute level.
- Sensing-communication fusion — running sensing and data traffic on one fiber core, so no dedicated sensing cable is required.
Frequently Asked Questions
Further reading
- Distributed temperature sensing — the measurement principle behind per-meter cable temperature profiles.
- Distributed acoustic sensing — how vibration detection covers gallery intrusion and third-party activity.
- Fiber optic sensor — background on EMI-immune fiber sensing near high-current cables.
- Optical time-domain reflectometer — the localization technique underlying meter-level event positioning.
Last updated: September 2026
By the Landsub Global Engineering Team
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