Figure. 5.4.17. - 69. Thermal image calculation with nominal conditions, example.
This described behavior is based into that assumption that the monitored object, whether cable, line or
electrical device has a homogenous body which is generating and dissipating heat with a rate which is
proportional to temperature rise caused by current squared. This usually is the case with cables and
objects while overhead lines heat dissipation is dependent of current weather conditions. Weather
conditions considering the prevailing conditions in the thermal replica are compensated with ambient
temperature coef cient which is constantly calculated and changing when using RTD sensor for the
measurement. When the ambient temperature of the protected object is stable it can be set manually
(e.g. in case of ground dug cables).
Ambient temperature compensation takes into account the set minimum and maximum temperature
and load capacity of the protected object and measured or set ambient temperature. The calculated
coef cient is linear correction factor which is presented with following formulas:
AQ-T257
Instruction manual
Version: 2.00
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