Real-time thermal monitoring of high-voltage (HV) power cables is being positioned as a practical way to unlock additional transmission capacity in renewable-heavy grids, according to technical findings presented at the CIGRE Southern Africa Regional Conference in Pretoria in October 2025.
Speaking during a data-driven power grids session, Athabile Lukhele of CBI-electric: African Cables said the integration of distributed temperature sensing (DTS) with real-time thermal rating (RTTR) systems could allow utilities to safely increase the usable capacity of existing HV cable assets by between 10% and 30% under favourable operating conditions.
The discussion comes as transmission constraints increasingly limit new renewable energy connections, placing pressure on grid operators to maximise existing infrastructure while maintaining system reliability.
Lukhele noted that most HV cable systems continue to be operated using conservative static or semi-dynamic ratings based on IEC standards, which assume worst-case environmental and installation conditions. In practice, factors such as soil moisture, seasonal thermal resistivity, cable spacing and fluctuating renewable-driven load profiles change over time, often leaving thermal headroom unused.
DTS systems use fibre-optic cables installed within or alongside power cables to provide continuous temperature measurements along the full cable route rather than relying on isolated point sensors. This enables the early identification of localised hotspots, joint defects, poor backfill conditions and external heat influences that may affect cable performance.
When combined with RTTR platforms, the temperature data is translated into real-time conductor temperatures and permissible loading levels, enabling dynamic cable rating based on actual operating conditions rather than fixed assumptions. The most thermally constrained section of a cable route determines the overall allowable load, ensuring safe operation while maximising utilisation elsewhere on the circuit.
RTTR systems can interface with SCADA and energy management platforms, providing operators with real-time alarms, hotspot identification and load forecasts to support dispatch and contingency decisions under variable renewable output.
Beyond capacity gains, Lukhele said real-time thermal monitoring also supports predictive maintenance and asset life management. Abnormal temperature profiles often emerge before conventional protection systems operate, allowing early intervention and reducing failure risk while continuous thermal histories support post-fault analysis.
While dynamic thermal monitoring does not remove the need for new transmission infrastructure, Lukhele said it offers a technically mature and immediately deployable means of extracting additional value from existing HV cable assets as grids transition towards renewable-rich operation.
