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I work on wind turbines, I am a troubleshooter. I have a problem on the turbine which I cannot solve so far I would like to ask the help of this community.

When turbine starts to generate, an unbalance appears on the 690V 3-phase system. This appears only when the turbine is producing. The phases are balanced when the turbine runs from the grid.

As the generator production increases, the difference on phase 1 gets bigger. The maximum I've measured on phase 1 was 422V to ground. The other two phases are stable 397V.

In the line of the production there is the generator, converter AC/DC and DC/AC, main reactor, filter cabinet and the 690V circuit breaker.

My question is, what could cause this unbalance? If you need more info about the system, just let me know.

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    \$\begingroup\$ Please supply a basic schematic (blocks for every component at least) I'm not sure from reading your text, where the voltage is measured. \$\endgroup\$
    – Ariser
    Aug 4 '19 at 14:47
  • \$\begingroup\$ My guess is there's a small single-phase power supply on phase1 which puts noise on that phase. \$\endgroup\$
    – Janka
    Aug 5 '19 at 13:58
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If there is a voltage imbalance at the point where the generator system is connected to the grid, there must be an unbalance in the phase impedance between that point and the point where the grid voltage is regulated or the point of common coupling with other suppliers and/or loads. If the circuit breaker where the voltage is being measured is the last piece of equipment in the line of production from the generator to the grid, the impedance causing the unbalance is not your equipment.

Rather than unbalanced impedance, the problem may be an unbalanced current load on the grid. The grid is telling you that you must supply part of that unbalance. Check the current balance.

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  • \$\begingroup\$ Wouldn't it be fairly normal for a grid to have an unbalanced current load? \$\endgroup\$
    – hekete
    Aug 6 '19 at 4:02
  • \$\begingroup\$ @hekete I would think some level of unbalanced current would be common, but I don't know what that level might be, how it changes over time and how a "typical" supply point might react. \$\endgroup\$ Aug 6 '19 at 13:36

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