Local line voltage
 

I had the Variac out today to run up my 21CT55 (not happy for another thread later) and the line side meter showed 130vac or so. I checked with my digi meter and a vintage Weston AC meter and got 129.6vac. Is that a bit high? I held the set to 115vac even though it was more like 120vac in the day. The local feed is 4k AC down to only 4 homes and a rural Telco CO.

Yeah, that is on the high side. Sometimes it depends on where you live. In my rural area they put transformers along the long stretches to boost the sagging voltage. If you live near one of those your voltage will be hot. I live off the grid so no worries for me.

150' from my xfmr. The Telco CO got a huge digital upgrade last summer and an new 3 phase xfrm set and a genny for outages. Big pull there.

I had similarly high line voltage at my home in Illinois. They checked and declined to do anything - I think they are mainly concerned with too-low voltage potentially damaging A/C units or other heavy motors. I haven't checked incoming voltage here in AZ in years, and don't recall what it was - just always use a variac on my CTC-5.

The transformers I mean are HV to HV, not HV to LV like the one that feeds your house. Not that it makes mu difference, they probably won't do anything about it. I'd report it anyway just to see. A variac is a good option.

I tend to buy saturable reactor/ VRT, voltage regulating isolation transformers to deal with line voltage issues. They'll take anything from 90-140V in and depending on vintage of the transformer spit out a constant 110, 117 or 120V.
Local line voltage fluctuates enough to cause repeat noticable blooming by me, and I worry about it harming my rare early color sets so those regulating transformers are my solution.

Actually power companies use a capacitor bank to keep the voltage up at the end of long lines. They are usually rectangular looking devices.
https://electrical-engineering-porta...s-do-perfectly
( I had a summer job with an electric utility during college with SCE&G.)
Yes, what you need is a resonant regulated transformer. They have a third winding with a capacitor on it.
They also provide isolation.

Just as an FYI, the parameter for line voltage requirement for power utilities is +/- 10% of nominal.

So you live on a 4KV circuit? Wow- that's old. That's what they started out with.
The new stuff is 13.8/23.9 KV. The 4KV transformers are usually dark gray and the 13.8 transformers are light gray. Also the new transformers are larger with larger insulators on them.
Most 4KV distribution is single phase and uses #6 hard drawn copper for the lines. The 13.8 stuff can be single or 3 phase. The insulators are larger and the lines are usually ACSR cable (Aluminum Covered Steel Re-inforced).
SCE&G still had some 4KV stuff out on the rural coastal island communities, so its still around.
Another device you might see on poles are OCR's. The oil circuit reclosers are automatic circuit breakers filled with oil. They are round with two insulators out the top.
Both capacitor banks and OCR's are used on 3 phase lines.
Did you know that up until 2007 Consolidated Edison in NYC offered DC to its wharehouse customers that still used DC elevators?

The xfmrs show 4k on the side. The triple is the new feed to Verizon CO near my house. The single one is the local feed to four houses only. And the meter shows 134.9 at my house two nights ago. 126.6 today.

Here in San Fran, there's a boatload of DC elevators dating back to 1906. The utility maintains a dedicated rectifier station just for them. The one in our building is a 1907 Otis, a working museum piece that still runs 24/7.

On a business flight once I met an elevator specialist who was flying on an emergency call for an elevator system. He told me that many buildings are unique, gear gets repaired but not replaced, and there is little uniformity even in the 21st century.

Called PECO today to inform them of a shattered 4k pole behind me. No visit so far. And the local AC is now 146+. It goes up in the evening and around 126 during the day. Do I possibly have a home issue? Bad neutral connection, etc?

You can check for a floating neutral by finding 2 different phases (a 240V outlet for a stove, dryer, welder, AC unit, etc is a convenient place to measure) and checking neutral to ground on each phase. Both phases should have close to the same voltage.

Over 146V is nuts and shouldn't happen on a 120V circuit.

That looks like 13.8/23.9 stuff to me. And that's ACSR cable up there. Could be a loading problem with the other customers on that transformer.
I have never seen swings like that! Voltage does go up and down thru out the dayparts due to loading but shouldn't be that dramatic.
They'll probably send an engineer on something like that. They surely don't want any complaints to the public service commission!

146V is high enough to risk serious damage to anything plugged in, in your house. Floating neutral is the most likely culprit, either on your end or the utility end. I'd suggest to unplug valuable items and fix this problem asap.

Been watching for a few days and still the same. Seems to be ok during the day around 127vac but climbs after 6pm eastern. About 5vac per hour. 135vac right now and climbing. Power failed two days ago and the genny went on. Smooth 117vac. Back on mains and it resumes. Went to my breakers and dropped one at a time to look for a local issue. No changes. Will pull the panel cover tomm and measure inside. Curiously, my digi meter shows the changes but an analog meter sits at 130vac. Most shut off inside but for window AC units. PECO call on Tuesday.

Sounds like it could be a problem with harmonics on the line?

1) Digital meter may be reading peaks instead of RMS
2) An issue could be if electronic gear is responding to these peaks - it would be interesting to attach a DC meter to the B+ in a piece of unregulated gear and see how much that varies during the day
3) Be prepared to show/tell the power co. what kind(s) of meter(s) you are using

Wayne may have it. The house connected items are visually stable. No flickers, sudden bright bulbs, window AC's choking, etc. I only noticed it after my 21CT55 was acting up on the line connection. On a variac it calmed down but I diagnosed a faulty RF modulator for that problem. A variac analog meter did show some excess on the line side. On the regulated side it was fine at 115vac. But what causes peak voltage to float up and down? Beyond my basic AC knowledge.

Measure across the two hots in your panel, and see if the 230V varies proportionally to the increase you're reading at the outlet. If it does that rules out the neutral as an issue.

It is entirely possible this is bad utility regulation, where the voltage rises excessively as AC units shut off for the night.

Power companies use ‘tap changers’ on long medium voltage lines to keep the day/night voltage within range. These are auto-transformers that adjust themselves, used in groups of three on medium voltage (13.8kv) lines. Capacitor banks are used to correct power factor. Similar to supplying DC in old cities, up to 1999 a power plant was supplying 25 cycle AC to mines and factories in SW Missouri and NE Okla, legacy from installations ~1910. I think Pennsylvania has railroads still operating on 25 cycle AC. There was a lot of 25 in early days, including Niagra falls.

Rockaway Beach, NY used to have dips down around 89VAC in hot summer months. Overhead lines and an old, poorly maintained system.
Hurricane Sandy in 2012 changed that. New utility, massive overhauls. Plus most customers had to install a new panel since it was underwater.

We now have a year-round constant 119-122 VAC. No smartmeters here either for now. Opted out.

When I went to Malta in 1991 the line voltage was all over the place. It's supposed to be 240 volts, but the lights brightness would be up & down like a yo-yo, the CRT TV's picture would shrink & lose frame lock at random, I didn't have a volt meter with me so don't know what the actual voltage was... Went again in 1997 & took my volt meter & the voltage was rock steady at 240 with just a couple of volts either side. Think there must have been an upgrade since my first visit...

I live in a small town that is 2400/4160v primary and have not seen the voltage issues that others are experiencing, I show 118V despite being on the same 69kv/4160v substation transformer as the nearby large plastics plant. Neighborhoods are dotted with the old black oval & round side bushing transformers fed with either hard drawn or stranded copper with many of the houses using exposed hard copper drops. I'm a lead at the plastics plant and run the 1000-ton presses, Springfield-1000 takes 1200A/phase at 480V with the extruder heaters taking over half that. The plant 4160 primary is fed by several runs of 5KMCM and secondary is 4 bus runs at 2500A/480Y for the large products area. The electric bill is over $100K/week.
I did measure my outlet voltage over the thanksgiving weekend as the plant was "cold" and it was running 118.9V on my Fluke 8010A

As antiquated as my local local power system is I have to wonder why others are having so many issues with high line voltages, 130V would be the upper limit. The internal power transformer of say a CTC-25 could withstand 150V on the primary but the horizontal output might not as this could introduce a runaway condition possibly arcing over the flyback or pushing the 6JE6 beyond its safe dissipation.
I have a T940 Magnavox with the NORM/HIGH line switch, clearly this was a concern back in the late 60's. Running I find +420V going into the filter choke and about 5.9-6.2V on the heater fuse to ground, normal but a rise to 130+ primary would push this to almost 7V and over 460V on the B+. Clearly makes a good argument for a 500VA Sola transformer as I doubt the utility is going to address anything below 140V calling it an isolated incident.