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I would scrap the entire installation and install a single, properly sized, listed ground clamp that has not been field-fabricated or field-modified like the two pictured. The top clamp has “stacked” washers/hex nuts that do not appear to be part of the original assembly, and the lower mess...

ASIDE: The (old) Westinghouse [EHD] and GE [TED] MCCB "frame books" listed single-pole interrupting ratings as 8660 amperes.

No one has cited this one yet… From IEEE C57.13 7.7 Short-circuit capability Voltage transformers shall be capable of withstanding for 1 s the mechanical and thermal stresses resulting from a short circuit on the secondary terminals with full voltage maintained on the primary terminals...

Are you sure you don’t mean ‘pilot relay’? See http://www.gedigitalenergy.com/multilin/notes/artsci/art15.pdf

Do a Google search on transformer ferroresonance. At least it may be something to rule out. IEEE std C57.105 §8 has some basic information on transformer susceptibility to ferroresonance.

You might consider something like a “Group-U” [440Δ - 220Y/127V 3ø, 50Hz] transformer listed at www.acmepowerdist.com/energy-efficient-transformers-three-phase.htm

Although somewhat dated, you may want to look over http://www.everyspec.com/NIST/NIST+-+FIPS/FIPS_PUB_94_33007/

Steve, don’t even-order harmonics indicate DC offset in the waveform? That would seem to present its own set of problems.

Check out back issues of EC&M magazine. { www.ecmweb.com } There have been numerous articles on triplen and other power-system harmonics. One caveat—the online material is without charts, photos or illustrations. You have to purchase the articles to get those.

Another provider is www.boltswitch.com

www.keybellevilles.com is one manufacturer, but beware of their healthy minimum quantities and setup fees. www.sandc.com has, in times past, filled smaller orders for me.

A de facto document is ANSI standard IEEE C57.105-1978 IEEE Guide for Application of Transformer Connections in Three-Phase Distribution Systems §7, that be of some help.

ISTR that, in North America, typical listed drytypes have clearance requirements stated either on the label or packed with the transformer.

An aside—from practical experience, voltage-mode imbalance [ANSI device 47] protection should only be applied to inhibit 3-phase motor starting—where current-mode relays [ANSI device 46] are needed to reliably interrupt motor running.

Another supplier is JST corporaton at http://www.jst.com

This doesn't directly answer your question, but here is a ~50-year-old account of the perils on LV ungrounded systems—as opposed to high-resistance grounded systems. This all-time classic description is detailed in a chapter on system grounding in Beeman’s Industrial Power Systems Handbook...

You may want to review the paper at www.neiengineering.com/pdfs/paper1JN.pdf. It also has been extensively discussed in this forum.

See http://www.tnb-canada.com/en/catalogues/online/industrial_MRO/pdf/c3/05en.pdf page 1 “Two-Hole Lugs – Standard Barrel Certified to 600V and Recommended up to 35 kV”. My understanding is that the >600V application is to facilitate taping; but otherwise identical.

  I think, per the formula in C37.99, that your scheme should detect open fuse conditions. Just make sure that the 59N relay is restrained for third-harmonic conditions.

As referenced by waross, in this day and age there is no valid reason not to use hydraulic-compressed slices with heatshrink covers. Both have been around for decades with well-proven reliability.