variable and high utility voltage

[electrofelon]

Commissioned a 25KW resi system in December last year. Client notices one of the inverters is kicking off. I go there today to see what is going on. The event log shows "utility overvoltage". I kill all PV and measure the AC and in under a minute I get a low of 242 and high of 250. I wonder if they need a few more voltage regulators on this line or one is not functioning properly. Its an old line and I think this house is near the end of it. Obviously PV cutting out due to high voltage limit is not earth shattering, but this is the first time I have had an issue. Ill call the POCO and see if they will do anything.

 

[Hv&Lv]

Depends on the regulator control.
if they knew you were connecting they may have their control set on bi-directional, which will not work. PV should be voltage following and the regulator control will continually step up in that mode. most controls have a Co-gen setting it needs to be on. Did the event log show what the voltage went to? Or what do limit do you have it set to trip offline?

 

[electrofelon]

Depends on the regulator control.
if they knew you were connecting they may have their control set on bi-directional, which will not work. PV should be voltage following and the regulator control will continually step up in that mode. most controls have a Co-gen setting it needs to be on. Did the event log show what the voltage went to? Or what do limit do you have it set to trip offline?

Unfortunately I do not have a lot of event info because the inverters are not connected to WIFI and they have limited internal storage of I think only a day or two. IIRC the standard high voltage setting is 264. My conductors are good, should only be getting 2-3 volts rise to the weather head, although the drop is a puny #2 of about 50 feet so right there is another 2-3.

 

[Hv&Lv]

If it’s just started I would check to see if regulators or controls have been changed out recently.
Someone may have left a control the same and put it in a different type regulator.
Example: a straight design with a control on inverted and no second PT can do some weird things
If you ride back toward the source you can see if the regs look newer or not.
POCO may or may not tell you.

 

[electrofelon]

If it’s just started I would check to see if regulators or controls have been changed out recently.
Someone may have left a control the same and put it in a different type regulator.
Example: a straight design with a control on inverted and no second PT can do some weird things
If you ride back toward the source you can see if the regs look newer or not.
POCO may or may not tell you.

Unfortunately this it an hour and a half from home so I am not familiar with the distribution there like I am near home. Ill try to get a request into the POCO to investigate.

I dont know if this just started or not, we only notice when the owner goes and looks. He is supposed to get some WIFI out there but hasnt yet.

I think 250V might technically still be in spec, but doesnt swinging from 242 to 250 in a short period indicate a problem?

 

[Hv&Lv]

Depends on loading.
a regulator shouldn't step that fast unless it’s one of the new coopers.
could be a regulator stepped one or two times and some load dropped about the same time. Especially with old copper Or really small lines.
that’s what a run bank setting is for in a regulator control.

 

[ShltAbyss]

Contact tech support and they will walk you through how to raise the inverter voltage limits. I've done this many times on Fronius and SMA inverters.

 

[electrofelon]

Contact tech support and they will walk you through how to raise the inverter voltage limits. I've done this many times on Fronius and SMA inverters.

Yes that is an option but I would like to avoid it if possible. I don't like the system voltage getting above 264

 

[electrofelon]

So an update on this: I called the POCO a while back and complained about high voltage. This was just the regular customer service number and she put in a request. I swear it wasnt like 45 seconds after I hung up that I got a call from the local POCO shop. Talk about the the fastest response from a POCO in human history. In short, they ended up replacing the transformer. I am curious if they up sized it from standard 25KVA for a single family, or its anything special such a having taps that they set a bit lower, but I havent been back there to see. Client says all three inverters have been working, and AC voltage is mid 250's when PV cranking.

 

[Hv&Lv]

like many others here, I get a ton of emails every day.
i really look forward to, and pay special attention to the ones From our daily checks.
we have a program that does daily voltage reads twice a day on EVERY meter on our system, and SCADA issues, like excessive regulator operations or recloser operations.

there are times I see voltages in the extreme upper or lower ranges. For example, i had one a week ago that was reading 190. Made a service order, guys went and checked... bad connection at the weather head on a temporary saw service.
Another example Is one I had that was showing between 260 and 280. The guys went to this house and found the bushing blown apart, but still holding. just guessing coils shorted somewhere inside.

the point I‘m getting to is that many POCOs are getting better at daily monitoring of the system with the advances in SCADA and smart metering.

Glad it worked out. It could have been they did an on demand voltage read and noticed a problem immediately. Things like that is the reason the script was written for our daily reads.

Thanks for the update.

 

[Electricmo]

Hey Hv@Lv what’s your regulators time settings usually set at? Ours here are set at 90 seconds I think. When we cascade them you have to be very careful to get them coordinated correctly. Not sure on how that changes the settings as it’s been along time since I have had to work on them.

 

[Hv&Lv]

Ours are set at 30 at the station, then 60 for the ones down line.(if any)
we have very few line regs for a utility. I think less than 30 line regs total for 32 stations

 

[electrofelon]

Hey Hv@Lv what’s your regulators time settings usually set at? Ours here are set at 90 seconds I think. When we cascade them you have to be very careful to get them coordinated correctly. Not sure on how that changes the settings as it’s been along time since I have had to work on them.

What is the time setting? Is that how long a given set point has to be reached and held before the tap changes? I didnt realize the time was so long..

 

[Electricmo]

What is the time setting? Is that how long a given set point has to be reached and held before the tap changes? I didnt realize the time was so long..

Once Voltage drops out of band width a certain amount of time depending on where the regulator is located on the grid. Time curves are usually set quicker down stream from the substations. Substation regulators are usually set for longer intervals.

 

[Hv&Lv]

Once Voltage drops out of band width a certain amount of time depending on where the regulator is located on the grid. Time curves are usually set quicker down stream from the substations. Substation regulators are usually set for longer intervals.

We are regulating from the station. what few line regs we have takes care of problem areas.
we have some that are set at +2 and turned off.
plans are to reconduct that circuit next year. Get rid of them all together.

 

[pv_n00b]

Commissioned a 25KW resi system in December last year. Client notices one of the inverters is kicking off. I go there today to see what is going on. The event log shows "utility overvoltage". I kill all PV and measure the AC and in under a minute I get a low of 242 and high of 250. I wonder if they need a few more voltage regulators on this line or one is not functioning properly. Its an old line and I think this house is near the end of it. Obviously PV cutting out due to high voltage limit is not earth shattering, but this is the first time I have had an issue. Ill call the POCO and see if they will do anything.

The ANSI voltage range for 120/240V services is 110/220 to 126/252 and that should be the normal operating voltage range. They are allowed to go to 110/220 to 127/254 for short periods and it's still considered normal. Often at the end of a distribution line, the voltages will be at the high end to make sure the service closer to the regulator are above the minimum voltage. Saves money on those regulators.