Recent content by davidbeach

Something has to detect the fault to close the UFES…. I don’t think it’s “or” but rather “and”. The relay for detection and the UFES for quenching.

From the test reports I’ve seen the transformer testing is done at ambient temperature and then corrected to the operating temperature. But those are in the size range of a few MW to hundreds of MW.

The image didn’t load for me, but looping cable in a vault means that when a termination or splice fails you still have cable to do it again without needing to splice in an extension. Termination/splice failures seem far more common than actual cable failures.

I don't know, 100ft right-of-way and a 150ft tall tree on the uphill side of the ROW. Fall-ins I don't think I'd want to be dependent on those two lines in that weather...

Hint: It's not through current...

Pretty sure they have interrupting ratings as well. But since there are interrupting devices that have interrupting ratings around 20kA or so indicating that the 20kA was a thermal (continuous current) rating rather than an interrupting rating removes ambiguity.

I don't know who might make them, but there are lots and lots of generator breakers on the low-sides of the GSUs. We used to have a 20kA generator breaker. 20kA as a thermal rating, not an interrupting rating. Plant was decommissioned a few years ago and the breaker's gone. Got other...

You cannot apply common sense and logic to the code provisions. You can, however, submit proposed revisions.

A typical splice will involve crimped connections and there will likely be tape used. Never seen it done where it wasn't done with a proper kit and all of the parts. But if there was any leakage current they'd blow themselves up. With a bit of luck and good relays with good trigger points you...

There are probably millions of 15kV class splices that spend most of their existence under water.

Stevenal is definitely on to something. Had an application where an air coil reactor was already being used between bus and 115kV cap bank to limit fault current to what a breaker with both cap switching ratings and fault interrupting ratings could handle. As available fault current went up I...

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...

Not breakers per se, but we have SF6 circuit switchers used as the NO (and the NC) for automatic transfer (auto throw-over) substations at both 57 and 115kV. Seems to work fine, certainly much better than MODs. We do, however, have very little lightning.

Yeah, you've got a bunch of fault current coming back from the transformer.

That would be called theft.