Open Delta phase rotation

[Electromatic]

My town had a partial power outage a couple of weeks ago, and, after power was restored, one pump station had reverse rotation from the utility. Two other stations on the same poco (utility) circuit weren't affected. The station that was reversed is the only one of the three that is fed by an open delta transformer.

I don't have my head fully-around open delta systems. Is there some strange way that they can change rotation?
The poco lineman/troubleshooter was flummoxed, and the engineer was on vacation. [literally]

 

[ActionDave]

Interesting question. I'm just a wire pulling grunt so I will be open to any correction but, open delta or not, I don't see how rotation could spontaneously change just because the power went out. Something had to change, wires got swapped somewhere.

 

[hillbilly1]

Most likely the utility made a mistake-tap somewhere and flipped a phase. I repaired a feed from a padMount transformer that got knocked off its pad by a car. The lineman said they don’t mark the phase connections at the transformer, so I would have to check on my end. Luckily, they got it back right.

 

[don_resqcapt19]

The utility did some upgrade work many years ago on a circuit the fed one of our town's deep wells. That well had a shaft driven submersible pump. The utility got the rotation wrong and the reverse rotation spun the shaft apart dropping the pump down the shaft. It took the well company over a week to fish everything out and put it all back together. The utility did pick up the costs.

 

[ptonsparky]

The phase monitors we used prevented accidental reversal, if installed correctly.