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Thermal dynamic modeling
On installed underground cable circuits
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The power of the thermal dynamic model developed by KEMA over the existing models for static and cyclic current ratings is that the actual operating and installation conditions and parameters are taken into account. As a result, the operations manager is able to load his cable circuit to its actual limits and the asset manager may postpone investments because controlled current (over)loading is possible without the risk of cable damage due to overheating.
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Initialization
During the initial temperature measurements of the cable under
actual loading conditions, the computer model tunes itself. It
calculates the temperature at the measurement point and compares it
continuously with the measured temperature. The result of the
comparison is used for further tuning of the model. After the
tuning, the model may be used without actual continuous temperature
measurements. The actual conductor temperature can then be
calculated based on the actual loading current.
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Temperature measurements
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Temperature versus time
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Operation
During operation, the model calculates the conductor temperature and in the case of controlled (over)loading it calculates the maximum duration permitted at the given load. With this information, the operator knows exactly how much time he has available to implement changes to improve the situation. In addition, the model calculates the maximum allowable peak current during peak hours, taking into account the previous loading history.
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Example of thermal dynamic modelling
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Economic results
By using controlled current (over)loading without subjecting the
cable to damaging temperatures, and by optimizing the use of the
infrastructure, investments can be postponed and savings
realized.
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Technical results
The actual results can be compared with the results predicted in the original engineering design specifications. This information can then be used to improve engineering practices. The information provided by the model permits optimum usage of existing cable systems, and the actual thermal conditions in the cable and the ambient soil are known, preventing a possible thermal run-away (drying out of soil).
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