High line voltage discusssion

[dcg9381]

As you guys always have good suggestions, ideas, and experience:

I have residential 320A 240V service, which feeds our shop and our house. We are on our own dedicated transformer which takes the 14KV line voltage down to 240V.

The shop has a PV array. The PV array has been sending me error notifications (and shutting down temporarily) due to line voltage that exceeds 264V. It's happening not every day, but about every other day at almost the same time, around 7:40am. It's happened 6 or 7 times so far. The array will reset when line voltage goes back under 264v, but I haven't been able to pull the actual logs from the device.

I called the local utility, they sent someone out (Jerry) - who is great, but isn't exactly a technical guy. He measured line voltage (normal operation) at 255V and said that the utility spec is "240V +/- 7%" - so 255V is within their "acceptable range". He did give me what seems like a bunch of hogwash - indicating that I'd see problems with appliances, HVAC, if I was getting over 264V, but I'm not sure that's right. He's also said no one else is complaining, but no one else is monitoring line voltage minute to minute.

He said that the utility line runs "hot" (255V) intentionally to address some down stream power issues.

Apparently our transformer is a transformer, not a regulator - meaning it's simply a step down on line voltage and does not regulate. Jerry says that they cannot adjust voltage output on a 240V transformer, they can only do that with 3-phase.

The utility asked me to adjust my inverter to accept line voltage over 10%. I can do this, but I declined.

They've escalated me to someone who has the capacity to monitor the actual 14KV lines that are coming in. That person said that their monitored lines have automatic adjustments, but they do not adjust minute to minute, so it's possible that my equipment can detect line voltage issues before they adjust.

Thoughts?

 

[cvairwerks]

Need to run some 24/7 data recordings with measurement rates faster than 4 per minute to see whats actually happening

 

[alfredeneuman]

I called the local utility, they sent someone out (Jerry) - who is great, but isn't exactly a technical guy. He measured line voltage (normal operation) at 255V and said that the utility spec is "240V +/- 7%" - so 255V is within their "acceptable range".

The American National Standards Institute (ANSI) lists the at maximum utility tolerance of +/-5 percent. = 228-252V.

 

[wyliesdiesels]

As you guys always have good suggestions, ideas, and experience:

I have residential 320A 240V service, which feeds our shop and our house. We are on our own dedicated transformer which takes the 14KV line voltage down to 240V.

The shop has a PV array. The PV array has been sending me error notifications (and shutting down temporarily) due to line voltage that exceeds 264V. It's happening not every day, but about every other day at almost the same time, around 7:40am. It's happened 6 or 7 times so far. The array will reset when line voltage goes back under 264v, but I haven't been able to pull the actual logs from the device.

Ive heard of issues similar to this before and the culprit turned out to be a bank of capacitors switching on at the wrong time.

I called the local utility, they sent someone out (Jerry) - who is great, but isn't exactly a technical guy. He measured line voltage (normal operation) at 255V and said that the utility spec is "240V +/- 7%" - so 255V is within their "acceptable range". He did give me what seems like a bunch of hogwash - indicating that I'd see problems with appliances, HVAC, if I was getting over 264V, but I'm not sure that's right. He's also said no one else is complaining, but no one else is monitoring line voltage minute to minute.

That all depends on the specs and tolerances of the appliance....

He said that the utility line runs "hot" (255V) intentionally to address some down stream power issues.

Apparently our transformer is a transformer, not a regulator - meaning it's simply a step down on line voltage and does not regulate. Jerry says that they cannot adjust voltage output on a 240V transformer, they can only do that with 3-phase.

The utility asked me to adjust my inverter to accept line voltage over 10%. I can do this, but I declined.

yeah thats correct. the transformers used for split phase service usually dont have secondary taps to adjust the output voltage. its a fixed turns ratio....

and a regulator is something entirely different, though it does have a transformer.... step-down transformers on poles or pads, for services, would never be regulators... that would be too expensive to deploy

transformers for 3 phase banks will often have secondary taps which allow adjustment of output voltage... but thats still not the same as a voltage regulator which auto adjusts its voltage output depending on voltage input...

The 14KV distribution line that feeds your transformer would have a voltage regulator on it at some point on the line....

They've escalated me to someone who has the capacity to monitor the actual 14KV lines that are coming in. That person said that their monitored lines have automatic adjustments, but they do not adjust minute to minute, so it's possible that my equipment can detect line voltage issues before they adjust.

Thoughts?

yup that would be done with a voltage regulator....

thoughts?

you need to get logs of these voltage spikes. Or see if they have a logging meter they can put on your service so they can see whats going on before the tech gets to your house...i definitely wouldnt adjust your inverter... 264v and even 255V is too hot for my PoCo's standards (5%)

 

[wyliesdiesels]

The American National Standards Institute (ANSI) lists the at maximum utility tolerance of +/-5 percent. = 228-252V.

Do all PoCos have to abide by that though?

 

[dcg9381]

Utility is going to install a logging device... I have inverter warnings - but it looks like monitored line voltage logs requires another device.
They are trying to get me monitored line readings upstream on the 14kv.

They confirm measurements of 255V at my meter - within their tolerances.

 

[wyliesdiesels]

I would get the extra device so you can compare logs with their logs/readings...

 

[alfredeneuman]

Do all PoCos have to abide by that though?

I don't know for sure.
The States all have their different Public Utilities Commissions, and that's the only National or State standard listed on a DuckDuckGo or Google search

 

[jeepxj]

Utility is going to install a logging device... I have inverter warnings - but it looks like monitored line voltage logs requires another device.
They are trying to get me monitored line readings upstream on the 14kv.

They confirm measurements of 255V at my meter - within their tolerances.

isnt that at the higher end of the 5% tolerance?

 

[theoldwizard1]

Forget the high line ! Demand a voltage logger at the meter. PoCo don't like to do it, but they will if you complain long enough and loud enough.

They will never ACT on your data.

 

[walta]

All the talk about the 14k line is an attempt to pass the buck to another department and put enough delays and roadblocks in your way hoping you will get frustrated and go away.

Call back and insist they put monitor your 240 volt today. Next week when the log shows over voltage insist they fix it today.

Walta

 

[bbbarracuda]

The utility I used to work for would monitor at the meter. I never heard of them monitoring the high voltage. That is monitored at the distribution substation.
But every power co. is different, so it may just be a matter of finding the right dept to get results.

 

[alfredeneuman]

isnt that at the higher end of the 5% tolerance?

Re: 255V?
240V X .05 = 12V
240V + 12V = 252V

 

[kursplat]

I called the local utility, they sent someone out (Jerry) - who is great, but isn't exactly a technical guy. He measured line voltage (normal operation) at 255V and said that the utility spec is "240V +/- 7%" - so 255V is within their "acceptable range". He did give me what seems like a bunch of hogwash - indicating that I'd see problems with appliances, HVAC, if I was getting over 264V, but I'm not sure that's right. He's also said no one else is complaining, but no one else is monitoring line voltage minute to minute.

He said that the utility line runs "hot" (255V) intentionally to address some down stream power issues.

ya, his getting "acceptable range" when he's there doesn't count. they need to install a monitor at your panel and record it for a few days. them "running the line hot", i.e. cranking up the regulators at the station because someone at the end of the line probably had low voltage, should not be your problem. they aren't doing proper voltage control. they need to add line capacitors on the circuit or reconfigure the circuit so it's not getting the line loss at the far end of it. as far as "no one else calling", see if you can enlist a couple of neighbors to check their voltage, and call at the same time you're having a problem. where i work the station regulators do change minute to minute based on the circuit load.

edit: where i work 254v is max acceptable for a 240v service

 

[Chilliwack Murray]

Are you in a strictly residential area or are there industrial customers in your area as well? It sounds like excessive power factor correction coming on at a set time like the start of a shift, before the loads require the full correction.

A facility that has a lot of electric motors will be charged a large penalty for poor power factor so they often install capacitor banks to correct the power factor. If these are energized before the motors are running they will cause the line voltage to rise. Capacitor banks should be staged to match the loads but often they are all on or all off.

 

[Innovate1]

255 V when he was there seems high to me. Years ago I went to a field site that had several of my companies devices fail, one after the other as replacements were installed. Power company claimed it wasn't their issue and it was a big finger pointing thing with no one wanting to take the blame and trying to say our equipment was bad. I rented a data logger and installed it. Told them to disconnect in 3 weeks and send it back to me. I recorded 660V peak voltages and ringing when some nearby power factor capacitors switched. Sent them the waveforms and never heard from them again. I am guessing the power company fixed their equipment.

Monitoring the high voltage line is not the answer. They should monitor the voltage at the meter.

 

[dcg9381]

255V is within their "acceptable tolerance" of 7%.
Utility engineers did get back to me yesterday. They apparently have some sort of upstream voltage regulator that was "programmed wrong" - they were able to figure it out via my inverter logs of high voltage...
So I think this is resolved (no further inverter warnings for 48 hours).

 

[rlitman]

255V is within their "acceptable tolerance" of 7%.
Utility engineers did get back to me yesterday. They apparently have some sort of upstream voltage regulator that was "programmed wrong" - they were able to figure it out via my inverter logs of high voltage...
So I think this is resolved (no further inverter warnings for 48 hours).

Sweet. Yeah, your report of a specific daily time of the problem should have been enough for them to send the right troubleshooter to fix the issue. And yes, since your pole transformer is not smart, this sounded like a problem on the HV side.

 

[jeepxj]

255V is within their "acceptable tolerance" of 7%.
Utility engineers did get back to me yesterday. They apparently have some sort of upstream voltage regulator that was "programmed wrong" - they were able to figure it out via my inverter logs of high voltage...
So I think this is resolved (no further inverter warnings for 48 hours).

i wonder what the program mistake was.

 

[rlitman]

i wonder what the program mistake was.

Could be a lot of things. My personal experience with a similar issue was caused by a hardware problem with a capacitor bank that would switch on and off at certain times. PoCos will tweak what tap is used on a HV transformer to account for resistive losses on HV circuits, and it's often time controlled. Say, to raise the voltage when water heaters come on as people take their morning showers and turn on their coffee makers.

 

[dcg9381]

They said it was programming on a regulator (as near as I can recall).
The POC does have "capacitor banks" they they say they can deploy during periods of high draw (usually starting in the AM) - apparently these are turned on and turned off as necessary with grid demand. That was their first suspicion, but that wasn't it.

 

[dcg9381]

Some technical clarification:

an overview of how voltage control and alarms work with in our substations.



Utility Control Center monitors the voltage and status of all substation equipment across our entire system in real time with alarms set to alert the Control Center as soon anything falls outside the set perimeters, very much like the inverter on your solar panels. The voltage alarm at substation is set to alert the Control Center if the voltage increases to 130.0 volts or declines 118.0 volts.



The substation power transformer’s voltage output is controlled by an electronic voltage control panel called a 90 relay. The 90 relay is programmed to maintain an output voltage of 125.0 volts (band center) with a 2 volt bandwidth (1 volt either side of the 125.0V band center). The 90 relay monitors the voltage on A-phase and adjusts the voltage either up or down if it falls outside the 2 volt bandwidth (lowers at 126.0V and raises at 124.0V).

If the 90 relay fails, there is a backup voltage lockout relay called a 59 that will prevent the transformer from raising the voltage to high or lowering to low. The 59 backup lockout relay is set to maintain the same 125.0 volt band center as the 90 relay, but with a 6 volt bandwidth instead of 2 volt bandwidth. It shadows the 90 relay and if the voltage reaches 128.0V or 122.0V the 59 relay will physically open the voltage control circuit to prevent further voltage adjustments and send an alarm to our Control Center who will dispatch a Substation Technician to investigate.

Substation power transformers adjust the voltage automatically by physically changing the tap/ratio of the transformer in a device called a load tap changer (LTC) mounted on the side of the transformer. The LTC can raise or lower the voltage by changing the tap/ratio of the transformer 16 times in either direction, raise or lower.

 

[MBfreak]

Thanks DCG for a good review.
My $0,02 additions FWIW.
The electromechanical tap changer on the MV side of the MV to LV transformer is restricted when it comes to number of tap changes over a set period. Usually restricted to 5-8 changes an hour. Maintenace interval of LTC on a typical distribution transformer is 10.000 operations.
If the MV to LV transformer feeds a LV network over large distances there may be a load adder algoritm in the 90 relay that sets a nominal voltage about half way out in the network. A consumer closer to the transformer gets a bit higher voltage and towrds the end the voltage can be lower than nominal.

All above relates to my experience. I have no real knowledge of US MV/LV systems.
Ola

 

[dcg9381]

So, this is happening "again". Almost every day since the beginning of last month.
I've also noticed an indicator light blinking on one of the overhead power lines in the evening (probably unrelated, as these warnings are in the AM):

What's the best way to get a 24 hour log (The line guys don't believe my solar array logs) of peak AC voltage?

 

[rlitman]

The only way to get the utility to accept a log of voltages is to have them install a logger. They may do it in extreme cases, but they probably already have something at their substation that says things are good enough.

 

[wyliesdiesels]

So, this is happening "again". Almost every day since the beginning of last month.
I've also noticed an indicator light blinking on one of the overhead power lines in the evening (probably unrelated, as these warnings are in the AM):

What's the best way to get a 24 hour log (The line guys don't believe my solar array logs) of peak AC voltage?

whats blinking on the pole? could be a lightning arrestor that took a hit. our PoCo has those on some poles

rent a fluke data logger...

 

[wyliesdiesels]

The only way to get the utility to accept a log of voltages is to have them install a logger. They may do it in extreme cases, but they probably already have something at their substation that says things are good enough.

substation voltages arent gonna tell whats going on at the end of the line. there could be a capacitor bank thats acting up. ive heard of that happening before many times. many of them are controlled with a timer to coincide with a large industrial customer firing up their plant. sometimes the timer is off or something else is screwed up and the bank comes online at the wrong time causing the voltage to go too high

 

[rlitman]

substation voltages arent gonna tell whats going on at the end of the line. there could be a capacity bank thats acting up. ive heard of that happening before many times. many of them are controlled with a timer to coincide with a large industrial customer firing up their plant. sometimes the timer is off or something else is screwed up and the bank comes online at the wrong time causing the voltage to go too high

BTDT. It took a LOT of up and back before I could get a troubleshooter linesman out, and after showing him graphs and high-speed data captures he was able to find arcing on one of the phases of a local capacitor bank for me. But I work at a data center, and we pay more for electricity in a day than I do over the course of many months, so we got a little priority here. As a homeowner, good luck.

 

[rancherbill]

I called the local utility, they sent someone out (Jerry) - who is great, but isn't exactly a technical guy. He measured line voltage (normal operation) at 255V and said that the utility spec is "240V +/- 7%" - so 255V is within their "acceptable range". He did give me what seems like a bunch of hogwash - indicating that I'd see problems with appliances, HVAC, if I was getting over 264V, but I'm not sure that's right. He's also said no one else is complaining, but no one else is monitoring line voltage minute to minute.

He said that the utility line runs "hot" (255V) intentionally to address some down stream power issues.

Hey you've been getting electricity rates for years. My guess you utility has not invested enough in infrastructure. Shareholder have got great dividend though.

 

[theoldwizard1]

Need to run some 24/7 data recordings with measurement rates faster than 4 per minute to see whats actually happening

The utility SHOULD do this for you, but you have to complain LOUDLY !

 

[Worsedog]

I have mentioned my similar experience before in other similar threads. I was experiencing a noticeable brightening of the lights in my house at random times.

Using a peak hold multimeter, I recorded surges of over 150v on one leg of the power. I went through all of the tightening/checking neutrals as poor neutrals can cause the same symptoms. Since there was no change, I called the poco. They sent a lineman and of course it was fine while he was on site, but he did recrimp the neutrals back to the transformer.

It made no difference, so I called back. They looked up the work order and told me they had determined that there was no issue. Not satisfied, I "stretched" my peak hold multimeter into a recording one and asked that they put there own on and monitor the voltage as it seemed totally random. I actually received a call from an engineer who basically told me I was wrong and there was nothing more to be done.

I really hate throwing down the lawyer card, but also didn't really appreciate being blown off like that. I then requested he connect me with the legal department so I could get the correct address for my attorney to send the bills to when I started replacing electronics and appliances due to the over voltage conditions I was experiencing. He then said they'd put a monitor on the meter.

The next day there was this very expensive looking Fluke monitor connected to the meter can. It was there for four days and I know it saw the surges as I experience several of the "brightening of the lights" during that time. On the fifth day it was collected and two days after that a line crew was replacing the transformer across the street. Apparently there was a problem and something could be done!

Make sure everything is good on your side of the meter and if so, raise hell until someone listens.

 

[wyliesdiesels]

I have mentioned my similar experience before in other similar threads. I was experiencing a noticeable brightening of the lights in my house at random times.

Using a peak hold multimeter, I recorded surges of over 150v on one leg of the power. I went through all of the tightening/checking neutrals as poor neutrals can cause the same symptoms. Since there was no change, I called the poco. They sent a lineman and of course it was fine while he was on site, but he did recrimp the neutrals back to the transformer.

It made no difference, so I called back. They looked up the work order and told me they had determined that there was no issue. Not satisfied, I "stretched" my peak hold multimeter into a recording one and asked that they put there own on and monitor the voltage as it seemed totally random. I actually received a call from an engineer who basically told me I was wrong and there was nothing more to be done.

I really hate throwing down the lawyer card, but also didn't really appreciate being blown off like that. I then requested he connect me with the legal department so I could get the correct address for my attorney to send the bills to when I started replacing electronics and appliances due to the over voltage conditions I was experiencing. He then said they'd put a monitor on the meter.

The next day there was this very expensive looking Fluke monitor connected to the meter can. It was there for four days and I know it saw the surges as I experience several of the "brightening of the lights" during that time. On the fifth day it was collected and two days after that a line crew was replacing the transformer across the street. Apparently there was a problem and something could be done!

Make sure everything is good on your side of the meter and if so, raise hell until someone listens.

only on an MWBC branch circuit. if its not an MWBC then a loose neutral would just cause the circuit to lose power intermittently

 

[Worsedog]

only on an MWBC branch circuit. if its not an MWBC then a loose neutral would just cause the circuit to lose power intermittently

Loose neutral on the entrance conductors can cause what I was experiencing. Was checking every neutral in the box overkill? Sure, but this is GJ and overkill is a religion.

 

[ttpete]

There's always your state's Public Service Commission. It exists because the utilities all have monopolies, The commission exists to monitor the utilities. Threaten to open a complaint if the utility doesn't cure the problem.

 

[wyliesdiesels]

There's always your state's Public Service Commission. It exists because the utilities all have monopolies, The commission exists to monitor the utilities. Threaten to open a complaint if the utility doesn't cure the problem.

too bad the CPUC is in bed with Profit Gouge and Execute (PG&E) in California

 

[ttpete]

too bad the CPUC is in bed with Profit Gouge and Execute (PG&E) in California

Too bad for you, not me.

 

[wyliesdiesels]

Too bad for you, not me.

not me either. i dont have profits gone elsewhere electric service.... we have a local special government district coop that is far far cheaper than profit gouge and execute's rates

 

[Norcal]

not me either. i dont ey have profits gone elsewhere electric service.... we have a local special government district coop that is far far cheaper than profit gouge and execute's rates

Unfortunately I am a PG&E, Pacific Graft & Extortion, customer, the municipal electric utilities like Redding, Ukiah, Gridley, and SMUD in the Sacramento area, are much more reasonable then PG&E. I can't remember the name of the district wyliesdiesels is supplied by.

 

[wyliesdiesels]

Unfortunately I am a PG&E, Pacific Graft & Extortion, customer, the municipal electric utilities like Redding, Ukiah, Gridley, and SMUD in the Sacramento area, are much more reasonable then PG&E. I can't remember the name of the district wyliesdiesels is supplied by.

Modesto irrigation district... summer rates are almost 10cents cheaper than Profit gouge and execute’s rates...

MID’s balancing authority is SMUD...

Then theres TID and Merced ID south of us...

TID powers my shop in ceres ca... and theyre cheaper than MID...

Dont forget about silicon valley power (santa clara) which gets power from OID- oakdale irrgiation district, dams, which are north east of modesto...

 

[83VillageRepair]

If you are on a lightly loaded feeder your own generation could be causing it. If there is no power flow the inverter raises voltage until power flow occurs or it trips itself out. Not saying this is the case but I have seen it before.