“Power lines are underground”
Thinking about this some things came to mind….
Is your 100a box fed by the main 200a service? Usually sub boxes or sub feeds have something from the main service being used in common… such as the ‘common’ or neutral side of the ckt. Also, it is not uncommon for the sub fed service to used the same ground conductor. And if only one conductor, neutral or ground is being split off to feed that 100a panel, the issue if it exists in either service will extend into the previous or latter service.
The advice to firm up connections in the service panels on the main busses and neutral or ground bars is very good info. Use good sense. Turn off the power before removing the security or safety plate and exposing everything.
The main feeds in a 200a svc can have either allen screws securing the two hots and one neutral, or a more standard fastener.
If the ‘main’ lines are at all loose, and the incoming cables are aluminum there is a goop that will aid connectivity and reduce oxidation.
Aluminum can be squeezed down to nearly nothing with some fasteners, make it tight and a wee bit, but no more.
Tightening the leads on each breaker may require a different type than a standard screwdriver depending on who made the panel itself.
Differences in potential even between ground rods can cause trouble in the home.
The Electrical contractor I worked for when we were building a Honeywell electronics engineering, manufacturering and testing facility many years ago had to have many power lines spec’d out and or dedicated. This meant a lot of ground rods were inserted too. Most rods were in the same general area. Some just a few feet away. Honeywell techs said they were getting feedback voltages on open circuits under testing. One of the older more exp’d Electrician foremen came up with the idea of checking each ground rod to each other rod. After the laughter the process ensued. Eventually we found between some of the rods as much as 5 or 6 volts disparity. We made make shift ‘inductors’ for each ckt/ground rod. And as non scientific as that sounds, it was enough to prevent the once found aberration, to being found no longer.
Even the density of the moisture within the ground can affect how well your grounding circuit will work. Keeping it damp helps. Trust me here. Its why GRs are 8ft long. They used to be 12. Then 10. Formerly copper, not just galvanized steel as so many are today. Grounds need to be firmly connected too. The moisture in the dirt is doing the connecting.
Grounding to plumbing used to be a good idea too. Back when it was all metal.
Hums or worse still, loud buzzes indicate an electrical issue usually surrounding grounds.
Loose or weak connections, are ‘resistive’ connections… not grounds. They will merely limit conductivity or prevent it altogether. They won’t introduce hum or buzz into the circuit which can be heard via very sensitive audio speakers or it could otherwise be seen with an O scope.
Grease, oils, heat, dampness, even invisible to the eye can cause grounds.
Underground cable runs are susceptible to lots of stuff. Even when ran thru conduit. Standing water. Critters. Bruised dialectrics or insulation can cut or scrape just enough off the main feeds to allow some conduction thru what is left of the insulation. Poor terminations at the feed down the block or where it juts off into your property could be a place that needs greater scrutiny.
Any yard work lately where something was planted altered or changed even slightly? Signs? Mail box? Trees? Sprinbkler system? Plumbing issues? Pool? If pool is present, don’t forget to remove it from the circuit. Timers? Exterior lighting changed or installed?? Fencing?
A ‘megger’ is used to determine the quality of an insulator on a conductor. Did your electricians Meg ohm the lines to check the insulation of each phase.?
One solution for a power line was stated, for CATV there are transformers that can be inserted into the line feeding the home, or at the modem. As with the previously mentioned power line fix, RWV.
Good luck.
