During erection stage of any industrial installation, despite the designer and project ingineerig good practice, the interest of the erection engineers are concentrated in the mounting, installation and connection as per project drawings and do not think at that stage in plant operation details. this behavior occasionally lead to the following problem:
A rigid prefabricated busbar interconnection between the 6/0.48 Kv 1500 KVA DY5 vectorial group transformer connected to the assosiated MCC were not coupled in phase rotation each other. What does the the engineer did ??. they found eisy to permut two phase at the primary side of the transformer to get the phase rotation, apparently the problem was over because they got AtoA, BtoB and CtoC coupled phase rotation in LT side and all motor rotation in the same way when this MCC should linked to feed other MCC.
Difficult arrived during the test and precommissioning to operate in parallel connection by a tie CB with other MCC and transformer. So no cero volts appearing between any phase of the other MCC source with similar charateristic.
THE MISTAKE: Permuting two phases of primary side of the transformer during erection time trying to find equal phase rotation for both MCCs, the vectorial group changed from DY5 into DY1 so no paralleling operation can be done with different group.
To solve this problem out, it was necessary to remake de prefabricated busbar
This problem some time come from erection period.
I hope this UNESPECTED tale be of the genaral interest for the forum members
Bye
The UNESPECTED II
Re: The UNESPECTED II
