Raytech WR14-R Instruction Manual page 131

Procedure for eliminating the magnetized state of a transformer
One option that can be taken to safely switch a transformer back on line and avoid a dangerous
and damaging situation is to apply a reduced AC voltage source and increase the voltage level to
the operating voltage level. Under controlled conditions this may be possible. However, this
undertaking may not be theoretically possible when energizing a transformer on site. Equipment
required to fully demagnetize a transformer in this manner is large and expensive.
or
A better solution is the new Raytech Winding Resistance Meter, WR-Series.
These easy to use systems are recognized throughout the World for Precision Winding Resistance
measurements. A unique and new feature built into the WR-series is the ability to Automatically
Demagnetize a Transformer core on site.
Avoid unnecessary damage and unsafe conditions when energizing a transformer; use one of the
Raytech WR-series instruments and be sure.
Parameters for demagnetizing
The Current of the WR series test system should be applied on the high inductive or High Voltage
side of the transformer. The potential cables from Channel 1 must also be connected.
The optimal demagnetizing current to be used is the same as the measuring current used during
Winding Resistance Measurement or the maximum allowed for the nominal current level of the
high voltage side.
Instruction Manual Winding Resistance Meter
Page 131 of 139
Type WR100 / WR50 / WR14