Service voltage swings

Wally
Wally Registered Users Posts: 11
This Fronius inverter records the Utilities 240V service max and minimum voltage for the day and it usually is about a 60 volt swing.
The min is about 214V and max about 274V.

Seems like quite a bit --- works out to 114% of 240V for the high and 89% for the low.
Is this in the normal range for a Service?

The inverter is tracking it OK and hasn’t shut down because of this, probably helps the output is only a short 6 ft run of #4AWG to the interconnection.

Comments

  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    Re: Service voltage swings

    The "allowed" swing is typically +/- 10%, meaning 216 to 264 (varies depending on the utility and local law). Yours is a bit outside of that range. The high Voltage is particularly troublesome as that would be 137 on household outlets and could easily shorten the life of appliances. No doubt the utility would check this and find it all to be "acceptable".

    Most likely the service transformer is too small. Good luck convincing the utility to do anything about it: they are notoriously reluctant to make any effort towards repairs unless they aren't actually selling you power due to down lines.
  • BB.
    BB. Super Moderators, Administrators Posts: 33,431 admin
    Re: Service voltage swings

    Interesting your GT Inverter has not faulted--Many will start to fault at ~260-262 volts (to allow for calibration errors).

    I would suspect that the inverter is not reporting the voltages correctly.

    Do you have a good digital volt meter or even a "kill-a-watt" type meter you can monitor your line voltage with?

    Over 264/132 volts can be a problem for appliances/lighting (reliability).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    Re: Service voltage swings

    Oh: could also be bad wiring between the service panel and transformer; high resistance in the line will cause Voltage drop when power is pulled from utility and Voltage rise when pushed from the GTI.
  • solar_dave
    solar_dave Solar Expert Posts: 2,397 ✭✭✭✭
    Re: Service voltage swings

    While my voltage swings has been less than that lately, about 240V to 250V, the frequency must be having glitches as the inverter will drop out and it is always when there is an abrupt change in Voltage either up or down. I suspect they are cutting in generation or rerouting transmission when this happens and the inverter sees the line glitch. It just starts its 5 minute countdown and restarts. It is usually both inverters but on rare occasion only one will drop.

    BTW I never see this in winter, but quite often in summer when their load is the highest.
  • Wally
    Wally Registered Users Posts: 11
    Re: Service voltage swings

    Probably not due to the service transformer being to small --- I think it is a 25 KVA unit, at least it has a big 25 sticker on it.

    I only export at the most at 11 KW’s so it should be able to handle that.

    I have checked the inverter’s reported voltage with a digital voltmeter and they agree with in a volt.

    Attachment not found.
  • BB.
    BB. Super Moderators, Administrators Posts: 33,431 admin
    Re: Service voltage swings

    You can figure out (roughly) if the problem is "local" resistance (your wiring, your local distribution wiring) or if it is more wide spread by measuring the current/voltage in the middle of the day (your 11 kW array pumping out current) and turning off the GT inverter for a moment and measure the voltage/current.

    Resistance = Vdelta/Idelta = (267 volts - 240 volts) / (50 amps - 10 amps) = 0.67 ohms (as an example)

    My home with 125 amp service:

    R = ~2 volt change / 10 amp from GT inverter = 0.2 ohm (estimated) from GT inverter to "Grid"

    And see what happens to your line voltage (i.e., does line voltage change by a few volts or tens of volts).

    If the voltage changes a lot during the test--Then your service/local distribution is undersized.

    If the voltage only changes a little, then your utility is having regulation/load issues up stream somewhere.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • peakbagger
    peakbagger Solar Expert Posts: 341 ✭✭✭
    Re: Service voltage swings

    My friend went through this with his utility last year. His unit would shut down on high voltage and not set a hard fault code so unless he was there he didn't know he had lost generation. Fronius gave him a code to up the allowable voltage range which helped. He called the utility and mentioned the Public Utilities Commission and they sent out a tech. They installed a power quality analyzer on his circuit and left it for few days. They admitted it was on their end. The town is rural and at the end of the line with a small hydro and a large capacitor bank for a large load plus there is a large chipping plant on the same local system. The hydro lost some controls at some point and they were dispatching it remotely and not realizing the impact to the local circuit. They did something to their end and the voltage range stabilized.