7. Manually execute Raise commands to step up the tap changer one step for all
transformers in the parallel group
8. Check that the value of BUSVOLT is below overvoltage blocking level OVPartBK
and above the undervoltage blocking level UVPartBK.
9. Set the control mode to Auto for each transformer in the parallel control group
The Master in the parallel group will issue a Lower command after time delay t1,
which will also be repeated by the Follower transformers in the group.
10. Set Transformer 2 to Master of the parallel group and T1 to Follower (in that order)
and repeat steps 7 to 10. Undertake this same test by setting each Transformer in turn
to Master
11. Note that voltage regulation will be mutually blocked if no transformer is set to
Master in the parallel group. To confirm this function, set T1 as Master and the other
transformers in the parallel grouper set as Follower. Without allocating a new
Master, set T1 to Follower and note the Automatic block state on the local HMI for
all parallel transformers
12. Restore T1 to Master of the parallel transformer group and ensure that control mode
for each transformer is Automatic.
12.1.5 Completing the test
After the test is completed and relevant disturbance records are saved to document the test,
go to Main menu/Clear on the local HMI and clear all LEDs, the process eventlist and
disturbances from the IED.
Section 12 1MRK 504 165-UUS -
Primary injection testing
292 Transformer protection RET670 2.2 ANSI
Commissioning manual
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