Do you think any of the products will go wrong when the “noisy wire” is draped over them? Might any operating electronics products be disturbed by being brought near to such a wire?
I do not think that this test will cause your products to go wrong. There are some operating electronics that this test might disturb.
I see what you are after with this test setup, but it is a very specific circumstance whose results are difficult to extrapolate from. I mean, that, for example, let's say that your test causes your LED devices to malfunction. Does that mean that the LED design is deficient, or that the test is too severe? Does this mean that other LED devices that you haven't tested will malfunction? Does this mean that your LED devices will malfunction after being installed by customers? You see, there is no calibration of this test to recognized or calibrated standards or to other real-world circumstances. It is, as I might call, a shot in the dark, so to speak. If your test result pointed to the need for a design change that costs money, how will you justify this expense?
Your test attempts to impose a broad spectrum of interference onto a test subject. The choice of square wave with a fast rise and fall time does indeed generate considerable spectral components and because there will be strong current flowing in your test wire, the spectrum components will likely have significant strength, however the method used to couple that energy to the device under test is not good. One way that you can improve this test is to open up your 30 meter wire by separating the two conductors and form it into a coil around the test subject. Most of the coupling will be through magnetic field, kind of like a transformer, and your 30m wire makes a poor primary. It will couple considerably more magnetic field if it is formed into a large loop that surrounds the test subject. Another way that you can make your test setup much more effective is to allow the square wave switching frequency to be variable and controlled externally. With this feature, you can sweep the frequency up and down to look for sensitivities that may not be apparent when using only one square wave frequency.
I believe that others perform calibrated testing for electromagnetic compatibility by generating one spectrum component at a time (ie. a sinusoid) and then radiating them, with significant strength, onto the test subject. When dealing with one frequency at a time it is possible to calibrate and know the field strength being imposed onto the device under test and so then be able to compare results to others.
This link offers a quick explanation, for others reading this thread, of what EMC is about.
https://www.emcbayswater.com.au/blo...romagnetic-compatibility-emc-testing-methods/
Your test falls into the category of susceptibility/immunity. Have you given any thought to testing for excessive emissions from your LED product? This is of greater concern to the community.