[RE-wrenches] Smart grid grid-connected compatibility

[Kent Osterberg]

Fellow wrenches,

I've got a question for those wrenches that have grid-connected 
inverters in locations where the utility uses remote meter reading 
technology - hey it's going to be everywhere soon. Are you seeing 
compatibility problems with grid-connected inverters and the utility's 
meter reading signals?

The utility here has been installing a remote meter reading system that 
uses TWACS. You can read about TWACS on the ACLARA website 
<http://www.aclaratech.com/AclaraPLS/Pages/specsheets.aspx> but they 
divulge very little technical information. For that you have to dig a 
bit to find that the TWACS signal is generated by firing a SCR through a 
small inductor that's connected L1 to L2. The firing happens near the 
zero crossing of the 60 Hz waveform and seems to be messing up a lot of 
devices including some microinverters. If you have data monitoring, the 
inverters react as if the voltage/frequency is out of tolerance and shut 
down for five minutes. The daily power graph has multiple steep power 
drops lasting five minutes at times when smooth continuous power is 
expected.

It would be good if we could identify which inverters have compatibility 
problems for various technologies.

-- 
Kent Osterberg
Blue Mountain Solar, Inc.
www.bluemountainsolar.com

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