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Forum Index : Windmills : Skystream 3.7 braking unnecessarily
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| gshteynberg Newbie  Joined: 08/08/2015 Location: Virgin IslandsPosts: 2 |
Hello all, I really hope that someone out there can help. I've been trying to understand why my skystream 3.7 starts braking when it reaches only 60 RPM. One thing I noticed the high Voltage DC bus when it not generating anything (345). Is this normal? We also have solar panels, could it be that the wind turbine is sensing the voltage produced by the solar panels? If so, could it be braking based on this high number? Any thoughts would be appreciated, thanks, Garriy |
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Gizmo Admin Group  Joined: 05/06/2004 Location: AustraliaPosts: 5078 |
Hi Garriy. Need some more info. Whats the Skystream connected to? A grid tie inverter, or rectifier and battery bank? Any model numbers would help too. Glenn The best time to plant a tree was twenty years ago, the second best time is right now. JAQ |
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| gshteynberg Newbie Joined: 08/08/2015 Location: Virgin IslandsPosts: 2 |
Hi Glenn, I've received a response (based on a data file I sent) from tech support. Perhaps you can help me understand it. "The turbine appears to be experiencing repeated events coded as event “30” which decodes as “DC Offset Error”. This is the text that should/would show in the “last event” field of the Quick Diagnostics tab in Skyview if you happened to be watching the Skyview software at the time a shut down occurs. The only other event showing in the data log is one shut down for grid frequency but this appears to be an anomaly as it doesn’t look like grid frequency goes outside the allowable range (then again, grid frequency can vary rather suddenly and a one-second interval probably isn’t enough to catch the actual shut-down value). The explanation of the DC Offset error from the engineer is as follows: DC Offset refers to the AC Grid connection and the symmetry of the AC signal. The AC signal is a sine wave – goes positive, then negative…. If it goes more one way then the other it has a DC offset by the amount it goes more one way then the other. It a bad thing from the utility perspective since it’s a waste of power. There is a limit Skystream has to detect (according to our certification) when putting out power and this is apparently exceeding that. It could be a problem with the grid connection itself – a transformer feeding the Skystream could be going bad and causing it. Other household appliances wouldn’t have any symptoms of the problem because they don’t really have to care about it, the way Skystream does. Alternately, it could be measurement or other error on the inverter in the turbine, which would require a replacement." The turbine is on a small island of St. John where the power company does not inspire confidence. So it very well may be the grid. Any ideas on how to figure this out? (A new inverter would cost $2k). Also, as a side note, the grid frequency DOES go beyond the allowable range -- but again we don't know whether it is the inverter or the grid, etc. Final detail -- there are 18 solar panels feeding into the grid as well, perhaps that's important. Any thoughts would be much appreciated! Thanks, Garriy |
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yahoo2 Guru  Joined: 05/04/2011 Location: AustraliaPosts: 1166 |
you can always turn the solar inverter off and find out if it still plays up or if it is braking at night it is not likely that the solar inverter is causing a problem. there is probably 6-7 groups of connections and switches between the turbine and the grid, I tend to eye them with suspicion and make sure they are maintained in good working condition. they may get hot under load a sure sign they are high resistance. there will be brushes and slip rings that can be inspected if the tower is down. Perhaps you could switch off all your appliances with switchmode power supplies and flouros and run some induction motors (bench grinder drill press) to see if that cleans the mains AC wave up. Beyond that i am a bit lost, I have never worked on a turbine that has the inverter inside the nacelle. No idea of the reliability of the sensors or the inverter itself. I'm confused, no wait... maybe I'm not... |
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