Mike:

 

Answer is no, I have not “developed a methodology for examining different GMD orientations that we can discuss at a PGDTF meeting”. 

 

My recommendation would be that someone perform a preliminary investigation into this with the objective of gaining a clearing understanding of the pros and cons of the various methods.  At a minimum, seems you should compare the “every x/30 degree” method to the worst case losses by region method (region could be weather zone, TSP service area, voltage category, etc.).

 

 

 

 

 

Ben,

 

The GIC flows posted are good evidence of localized impact of the different orientations because the max GIC for each transformer did not occur at the same orientation.  Have you developed a methodology for examining different GMD orientations that we can discuss at a PGDTF meeting?

 

Thanks,

 

Mike

 

 

PGDTF:

 

The attached is FYI.

 

 

 

Team (feel free to pass this e-mail around):

 

Justification to examine more than 1 orientation:

 

1.       Please read (less than 1 page of reading)  Section 3.3 of NERC GMD Planning Guide:  https://www.nerc.com/comm/PC/Geomagnetic%20Disturbance%20Task%20Force%20GMDTF%202013/GMD%20Planning%20Guide_approved.pdf

2.       Notice the NERC time-series data for the benchmark event is provided with data points at 10 second intervals for a 30 hour event.  Within most of those 10 second intervals the storm changes orientation significantly.  For example from time point 56,590 seconds to 56,600 seconds, a 10 second interval, the storm changes orientation by 178 degrees. You can find this 10 second 30 hours Excel data on NERC’s website under Benchmark GMD Event in this location: https://www.nerc.com/comm/PC/Pages/Geomagnetic-Disturbance-Task-Force-(GMDTF)-2013.aspx?View={2411fa34-593e-4b21-be7a-245dcb384c5d}&SortField=Date&SortDir=Desc

 

Conclusion.  If we expect outages to produce multiple system topologies during a presumed 30 hour event, we are also likely to experience system reactive losses that are very different than system reactive losses that are produced by a base case with all facilities in-service.

 

This is the point I was attempting to communicate yesterday during our discussion of Orientation 2 in the draft Vulnerability Assessment Scope.   I walked away feeling that Mick Juricek understood this point clearly but not feeling like others did.  Whether you agree that we should examine losses for more than 1 orientation or not, I hope this will at least clarify why I am concerned.

 

 

 

A. Benjamin Richardson, P.E.(Colorado) Transmission and Interconnection Studies 2705 West Lake Drive Taylor, TX 76574 O: 512-248-4505 | M:720-470-3643

 

 

 

 

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