Transformer Winding Temperature Indication CT Ratios

[thermionic1]

So I was checking out a new large power transformer and I'm wondering in the day and age of Electronic temperature monitors replacing the traditional analog gauges and heaters, why do the CT ratios seem like they are specified for older equipment. The Electronic temperature monitors can accept a wide variety of ratios. Maybe it's just my utility doing this? I think we had 2667:5 for one winding.

 

[davidbeach]

Stick with the weird ratio. Makes it easier to recognize that you have a CT that can't (shouldn't, anyway) be used for anything else. At some point added transformer differential to an older substation, probably replacing fuses, and used the one available CT on the low-side bushings and then to make things worse added aux CTs to get back to some sort of normal ratio. Took a long time to have a fault close enough in, but when it happened there was significant saturation of that monitoring CT/aux CT combo and the diff tripped for a through fault.