The online measured, distributed temperature information of the monitored cable system is especially valuable for dynamic rating. LIOS provides an integrated Real Time Thermal Rating (RTTR) evaluation via a well defined interface between its data visualisation software and a commercialised cable ampacity program. These two technologies are efficiently combined to produce a system capable of computing the future cable ampacity based on real-time temperature measurements. The actual maximum temperature reading of each configured cable section and the actual electrical current reading are evaluated for dynamic cable rating based on IEC standardised methods (mainly IEC 60287 and IEC 60853). When the geometry of the installation is not included in the IEC standards, the RTTR evaluation uses finite element methodologies to complement the IEC calculations.

The RTTR engine computes the current-carrying capacity (or ampacity) of underground cables in steady and transient states. Cable operators are especially interested in  transient simulations to estimate the current that can be safely transferred from another circuit due to emergency situations (maintenance, outages, faults, etc.). Typical situations include emergency ratings for 20 minutes, three hours, 24 hours and up to one week.

Power cable monitoring combined with dynamic ampacity rating provides valuable data to operators:

• Steady State Operation – Power cable conductor temperature at the core of the conductor
• Transient Operation - Emergency ratings,  transient calculations for Time, Current, Temperature

Modelling Capabilities
Virtually every cable construction available in the market can be modelled: one-core, three-core, sheathed cables, concentric neutrals, armoured cables, screens, shields, beddings, servings, jackets, combined sheath, etc.  Most of the installation types can be modelled: duct banks, backfills, directly buried, buried ducts, buried pipes, cables in air (including groups of cables and riser poles) and cables in tunnels.  The installation may include adjacent heat sources/sinks such as steam or water pipes. Unique is its ability to model several materials with different thermal resistivities, for example: stratified soil layers, multiple duct banks and multiple backfills.
Furthermore, the RTTR system can provide continuous and automatic adjustment of calculation parameters such as (ambient temperature, thermal resistivity, etc.).

RTTR is also known as "Dynamic Feeder Rating" or "Cable Ampacity from Real Time Temperatures" and several abbreviations are also common in scientific publications: DRS, DCR, CART, RTR, DFR

 Download brochure on Real Time Thermal Rating