Figure. 5.4.23 - 112. Thermal image calculation with nominal conditions: single time constant thermal replica.
The described behavior is based on the assumption that the monitored object has a homogenous body
which generates and dissipates heat with a rate proportional to the temperature rise caused by the
current squared. Installation conditions considering the prevailing conditions in the thermal replica are
compensated with the ambient temperature coefficient 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.
The ambient temperature compensation takes into account the set minimum and maximum
temperatures and the load capacity of the protected object as well as the measured or set ambient
temperature. The formulas below present examples of the calculation of the ambient temperature
coefficient (a linear correction factor to the maximum allowed current):
A
AQ
Q-M257
-M257
Instruction manual
Version: 2.07
© Arcteq Relays Ltd
IM00021
225
Summary of Contents for AQ-M257
Page 1: ...AQ M257 Motor protection IED Instruction manual...
Page 2: ......