4–242 845 TRANSFORMER PROTECTION SYSTEM – INSTRUCTION MANUAL
MONITORING CHAPTER 4: SETPOINTS
Thermal Elements The 845 thermal elements include Hottest-spot temperature, Aging Factor, and Loss of Life
elements. The computation of these elements follows the IEEE standards C57.91-2011
“IEEE Guide for Loading Mineral-Oil-Immersed Transformers”, and C57.96-2013 “IEEE Guide
for Loading Dry-Type Distribution Transformers”. The computations are based on
transformer loading conditions, ambient temperature, and entered transformer data.
•Refer to SETPOINTS > SYSTEM > TRANSFORMER > GENERAL and enter the
transformer data used in the computation of Hottest-Spot winding temperature,
Aging Factor, and Transformer Loss of Life
•Refer to SETPOINTS > SYSTEM > TRANSFORMER > WINDING 1(2,3) and enter the
windings data used to compute the transformer loading
The transformer winding settings are used for calculation of the winding nominal current,
and the load loss at rated load. The ratio of the actual load to the rated load K is used in the
Hottest-spot temperature computation. If the load loss at rated load is not available from
the transformer’s test report, use the following formulae to calculate it.
P
R
=I
n(W)
2
*R, where I
n(W)
is the winding rated current, and R is the three phase series
resistance.
•Refer to Setpoints > System > Transformer > Thermal Inputs menu, and select the
inputs for Ambient temperature and Top-Oil temperature. If no transducer is available
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