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b. Connect the grounding bolt M12 (No. 19 wrench, torque 50～60N.m.) on the transmission
mechanism protection box to the transformer oil tank.
10.2 Test in transformer factory
10.2.1 Operation test
Pre- operation must be carried out to check the mechanical functions of the tap-changer and the motor-
drive mechanism before the transformer is energized.
When the first time of operating the on-load tap-changer after the transformer has been dried, make
sure that the tap selector is completely immersed in transformer oil and the diverter switch oil
compartment is filled with oil.
When operating the tap-changer for the first time after the transformer is dried, make sure:
1. The tap selector is completely immersed in transformer oil and the diverter switch oil compartment
must be filled with oil;
2. During the operation test, the tap changer must go through the complete operating range;
3. Make sure that the MDU’s and tap-changer’s position indicators (observation window on the tap-
changer head) show the same position in every operating position.
4. Check the electrical and mechanical end limit functions at two end positions (Please refer to MDU
instruction manual).
10.2.2 The electrical test of the transformer
Continue to operate the tap-changer WITHOUT OIL will cause damage to the tap-
changer！
If the connection between the tap-changer and the MDU is improperly
aligned, continuous operation will cause damage to the tap-changer.
There is explosive gas under the tap-changer cover, in the connection
system, oil conservator and the outlet of air dryer. The flying parts and
the high temperature oil splashing to the outside will cause fatal and
Please confirm: there is no open flame, heat source or electric spark (such as
electric spark produced by static electricity) within its direct contact range, and
there is no possibility of generating them. It must be ensured that the tap-changer
test must be carried out by professionals in accordance with the test procedures.
WARNING:
If the connection between the tap changer and the motor-drive
mechanism is improperly aligned, continued operation will cause
damage to the tap changer.！
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