JBD...
1) ALL instruction omits 2nd order and 3rd order effects, typically entirely, otherwise... until the end. This includes even advanced college courses. Launching off into such side-tracks maddens the instructor and confuses the students.
Example: the Law of Gravity. At the start, Newton's law is presented as a two-body problem. The math is challenging even then. So much so that Newton invented calculus to solve the matter. (His notational conventions have never caught on. Leibniz's notations did. Centuries later the matter is still argued.)
The first scientist, Cavendish, to 'weigh the Earth' set up his apparatus to cancel out all other gravity influences so that he could resolve the issue to at least the first decimals. To do so was brutal. Too early for a Nobel, he would've received one, hands down, if the prize yet existed.
Yet Newton's law is written to cover all matter at all times and to all distances. To do so with even three-bodies is considered upper division work, really brutal.
No-one has ever used classical math to solve even the four-body problem. NASA had to use computational mathematics... settling for an approximation that had enough accuracy to get the job done. In all calculations, the distant stars are entirely neglected, even though the theory says that they're influencing events across the light-years.
Gravity is also a 'central force.' For calculations it can be treated as if it is emitted from a single point most of the time. This notion entirely breaks down when neutron stars approach black holes. Which brings us to some comprehension of the limits to 'theory projection.' When anyone is working from simplifying assumptions idealized systems and interactions that person has to be on the lookout for limiting conditions. Sometimes these situations can only be approached via 'thought experiments.' It was by this means that Einstein revealed that Newton's physics completely broke down at extreme velocities. Later it was proved that Newton's physics could not fit the extremely small, either.
In both cases, the scientific world was stood on its head. They'd found that everything that they assumed was universally true wasn't!
2) In all my days I've NEVER seen an engineering course side-track off into 2nd and 3rd order effects unless it HAD to. Generally, no-one can build anything based upon such deviations. Instead, in all of the practical arts, the attempt is to isolate upon one, dominant, effect (hopefully linear) and exclude/ dampen other factors.
Thus we have circuits designed as approximations, followed by peg-board mock-ups, which are then tuned by 'decade boxes' and 'pots', monitored by 'scopes until the results satisfy. I had a good buddy who earned his keep doing that. In his case, he was stomping out glitches in high frequency DC switching circuits. At every turn he discovered that he needed to provide additional grounding ultimately for each signal line. You'll see that he was not alone: all of the modern pin-outs for CPUs feature endless grounding pins. The DC impedances can't be suppressed any other way. (He almost went insane trying to cure his state of the art motherboard.)
Under no circumstances should anyone think that the industry actually sits at a chalkboard and directly calculates the final production circuit.
3) No sales literature is EVER going to spout off product limitations. That's poor salesmanship. In the case of surge suppressors, the impedance issue is soft-peddled. I've never seen any cut sheet that explained the physics of E & B fields.
%%%
Going through the pdf linked:
3.6 (5) Trim the [CT lead] wire to the approximate length to avoid coils of excessive wiring.
Said coils are at risk of picking up signal contamination. The E&B fields never let up for a second.
Pg 16
Failure to install CT's in the correct orientation and on the correct phase will lead to inaccurate meter readings...
Being a signal analysis circuit that's been factory balanced, it's touchy.
Pg 20
A: Meters are tested and approved for accuracy [trimmed at the bench] with CT's installed in the correct orientation. Installing CT's backwards [inverted] and inverting [flopping] the terminal connections has a slight affect on meter accuracy.
This is further proof that the factory is concerned about 2nd and 3rd order effects. In this case, the only thing that could be at issue is the orientation of the leads as they entered and left the B fields. Because the entire nature of CT circuits is to amplify signals, the factory won't even stand behind even such a trivial shift in bias. This is another tip that the circuits are tuned. (Trimmed with variable resistors, 'pots')
The encapsulation evident in the CT's shows that whenever the factory can shield the CT's they do so.
The CT's that lack shielding are plainly dimensioned for plain vanilla bus bars rising vertically in CT sections. By their very geometry, they suppress the contamination of the adjoining bus bars. They face the flats of the bus. This is not only cheaper to wind, but figures to provide a sweeter signal.
The influence of the adjacent bus bars is still there, it's just that the Inverse Square Law makes their impact of no importance to readings within the range of accuracy. So, they're never brought up as an issue. The very construction of the switchgear is highly engineered so as to suppress all side effects. This is but a part of getting it listed by UL.
For example, ferro-magnetic materials are ALWAYS influenced by B fields. Switchgear is constructed with just such materials! To stop the box, itself, from bleeding off too much energy, clearances are built into the design. Because of the Inverse Square Law, it does not take too much for this issue to be completely suppressed.
It rises its ugly head during massive circuit faults. Hence the use of bonding bushings along the axis of all GEC's. In such events, the inductance [choking] effect of the conduit has to be suppressed by making it a co-conductor. (The bonding bushings do that. They remove the B fields from the issue, the jolt will travel via the E field into the earth.)
In the extreme form, inductance into the eddy currents of ferro-magnetic materials is used to melt iron! Such gadgets use massive current flows tuned to a sweet frequency and shielded, lest they do crazy things to every other object nearby.
The CT in the image looks like the installer came close to pulling off this trick.^^^
If he actually bonded the CT core to the neutral... bad things would happen. He, by so doing, had made the core part of the E field instead of the B field. Yikes. Such steels are not designed for low resistance! Pulsing juice would be enough to explain everything. This would be a '1st order effect, BTW.
I put this at the top of the list, because it doesn't look like the actual CT leads are fried, though I suspect they were kicking out very weird readings, too.
