7 Operation
Maschinenfabrik Reinhausen GmbH 2019244 5163667/06 ENETOS
®
IM
3. Set parameter.
4. Press the Accept button to save the modified parameter.
7.21 Overload (optional)
With the optional overload function, you can determine the theoretical over-
load capability of the transformer and the loss-of-life caused by this. The
value can either be calculated in accordance with the IEEE Std C57.91 or
IEC 60076-7 calculation model.
NOTICE
Damage to the transformer!
An impermissibly high or long transformer overload can reduce the dielectric
strength of the transformer oil and damage the transformer insulation. This
can lead to tap short circuits and the transformer failing. Note that the per-
mitted overload is calculated based on a theoretical model in accordance
with either IEEE Std C57.91 or IEC 60076-7 and, as a result, deviations to
the actual conditions at the transformer can occur.
► Ensure that the transformer's protective devices and equipment are func-
tional.
► Also monitor the measured values for temperature, power, and gas build-
up during operation of the transformers within the overload range.
Measurement uncertainties
The transformer's moisture in oil value is also determined for the calculation
of the permissible overload, in addition to the measured temperature of the
top-oil and the calculated hot-spot temperature. The bubbling temperature is
calculated from the moisture in oil value.
The calculation of the bubbling temperature is only sufficiently accurate if the
transformer was in operation for a time period longer than 60 days and
loaded evenly.
If your transformer has been out of operation for a long time and in operation
for less than 60 days, or if your transformer is subject to large load devia-
tions, the device cannot calculate the permitted load precisely.
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