Grid Impedance

pcguy2upcguy2u Solar Expert Posts: 139 ✭✭✭
I have read that inverters can have some difficulty selling if your connection to the grid is more than X miles from the last 120KV (or is it 60KV) power station/transformer.

Anyone have any experience here?



  • BB.BB. Super Moderators, Administrators Posts: 32,642 admin
    Re: Grid Impedance

    I think we have seen a couple installs here where a long AC run from the GT inverter to the main panel was causing problems--along with utility power being a bit on the high side already (utility cranked down voltage in one case, Enphase installer adjusted maximum voltage set point in another--if I recall correctly).

    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • RCinFLARCinFLA Solar Expert Posts: 1,460 ✭✭✭✭
    Re: Grid Impedance

    I have not heard of a specific issue. I would guess if the GT inverter trips off on the grid impedance test then there would be a great deal of AC line voltage fluxuation to general loads within the premise. That would also trip off the GT inverter.
  • Ralph DayRalph Day Solar Expert Posts: 978 ✭✭✭✭
    Re: Grid Impedance
    BB. wrote: »
    Enphase installer adjusted maximum voltage set point in another--if I recall correctly).


    I think that was me. The voltage drop on the feed from the transformer to the panels caused the voltage to rise above 255vac when feeding power in. Enphase re-programmed the inverters via the monitoring Envoy to the high end of their design parameters (260vac). No problems in over a year at this level. The voltage at the combiner panel is usually 250-255vac.

    To code, but actually undersized feed made me batty for a while. My installer showed me some figures using heavier feed lines on another installation so I realized there was no sense ($) in replacing the #6 with heavier cable...just learned to live with 1% less revenue:grr

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