Synergi-->OpenDSS underground section bug

[NicolasGensollen]

Bug discovered when converting underground lines from Synergi to OpenDSS.

In this situation the input is an underground section where the wires are defined as for overhead lines but the spacing has negative heights. This is parsed into DiTTo in the exact same way the overhead lines are parsed. When writing to OpenDSS, this is exported as a LineGeometry with negative heights which raises the following error when running power flow, basically saying that the heights of the conductors should be >0:

'Error 325 Reported From OpenDSS Intrinsic Function: \r\nTVsourceObj.CalcYPrim\r\n\r\nError Description: \r\nMatrix Inversion Error for Vsource "source"\r\n\r\nProbable Cause: \r\nInvalid impedance specified. Replaced with small resistance.\r\nError Encountered in Solve: Error in LineGeometry.geometry_2: Conductor 1 height must be  > 0.'

I'm still unsure of how to fix this. The easy way would be to output those underground sections as linecodes even though we have all the wires and spacing information. We could have a condition like "If the height of at least one conductor is negative for this line then output it using a linecode" or something equivalent. The other way (probably harder) would be to model the underground section in OpenDSS using the wires and spacing. I'm unsure of how to combine CNData or TSData with spacing information, but if someone knows how to do that, I'd be happy to work on adding this capability to the OpenDSS writer.

[NicolasGensollen]

@tarekelgindy, I believe this will be solved once your branch is merged.

[NicolasGensollen]

This should be solved by #200. Closing for now.