Due to a hangover from the days of us having our own power station all the 11KV boards were BYR. We used 550V on the plants with the same rotation.
Then two new plants were build which were using this weird 433V. Some genius decided the rotation should be RYB. They were separate from the older plants so it didn’t matter.
Then it came to major alterations to one of the old plants. It was to retain 550V for some parts, 433 for the new stuff. Me being the resident idiot got lumbered with the job. First question, which rotation? Because it was overlapping with old stuff we went for BYR.
Again not really a problem as they were separate entities or so we thought. The plants spread out as they tend to and started to overlap. I got saddled with rebuilding a switchroom with 550V BYR, 433V RYB and 433V BYR. I was going dizzy! To add to the confusion the two 433V feeds could be interconnected.