Originally Posted by DanPackMan
The post you refer to said 'imepedance of utility", you are modifying it and saying "impedance of utility line". They are not necessarily the same thing, as one might look at 'the utility' as 'system' that has effectively zero impedance at the high side of the distribution transformer, or simply put effectively an infinite source of power. So, you can tell us if you intended one or the other.
First, we end users see the "system" as your definition of "high side of the distribution transformer" THROUGH the TRANSMISSION LINE. So we end user see the transmission line. Even power line has to be looked at as transmission line( as they correctly named it Transmission Line).
Second, Even the distribution transformer is very low impedance......AT 60Hz, it's high impedance at the noise we are talking about at about 40KHz with high content of harmonics.
Low impedance doesn't kill EMI, or prevent noise. A noise current forced into a high impedance circuit will result in a higher power noise than that same noise current forced into low impedance circuit. Power transmission and distribution lines are high power lines, and comparatively any induced noise will likely be very low power and insignificant.
I thought you are very familiar with electromagnetic. radiating noise is from current, the larger the current, the higher the magnetic field DENSITY (B) generated, so the lower the impedance at the termination, the more noise it radiated.
But again, its all meaningless unless you discuss WHAT NOISE you are concerned with and WHERE the noise if from. Noise comes in different forms. Injected, induced, thermal, mother in laws, etc...
That show you never read the post, we were talking about noise from those small SMPS AC to 9V/12V converters so common now a days and motor inductance kick. Read the thread!!!
The discussion had ended, I gave the likely cause of problem into the transmission line( power lines) by SMPS/motor/computer etc. and how it generates noise magnetic field, how a bad designed amp pick up the magnetic field in POST #59
. Also the easiest way to block the EMI from the line by an EMI filter.
In POST #60
, I showed how to design the amp to mitigate noise pick up where I already design and built into my amps. These are well covered in books on Signal Integrity.
Let's just end it here, I don't want to get into argument anymore.