On 22 May 2016, I ran a guest post from Bill Harris of the Foundation for Resilient Societies Board of Directors, which criticized the NERC regulatory process. The post below is Frank Koza's response.
Mr. Koza is the Executive Director of Infrastructure Planning at PJM Interconnection. I heard Mr. Koza's talk, Space Weather Power System Impacts and PJM Response, at the Space Weather Workshop I've been blogging about since April. That talk was also criticized in Mr. Harris' piece. Mr. Harris' original post can be found on my blog here.
Response to Bill Harris
The NERC standard (TPL-007), as drafted, is using the best, highest fidelity data available to establish the GMD benchmark event. Yes, the data is from Scandinavia, but it comprises magnetometer readings over the span of 15-18 years from a relatively dense network of measuring devices. The frequency plots from this data provide a very consistent set of results that were conservatively extrapolated to get to the 1-in-100 year probability benchmark electric field. No better set of data exists for this purpose, and certainly none from North America. There is no inclusion of coastal effects in the benchmark determination because the data to document such effects with the necessary rigor do not exist. There may be agreement that there are coastal effects, but the supporting data doesn’t exist. With additional research, it is possible that such data may become available in the future, at which time the benchmark could be modified. Contrary to Mr. Harris’ claims, the NERC standards drafting process followed the data.
The variation of geomagnetically-induced electric fields with geomagnetic latitude is based on the above data which shows a clear reduction of the electric field as the distance from the polar areas increase. Routine observation of the actual magnetometer readings during space weather events reinforces the data that was used to establish the alpha factor. Again, the NERC standards drafting process followed the data.
The development of the 75 ampere threshold for detailed transformer thermal analysis is based on a large number of simulations performed on multiple transformer thermal models. In this case, there is no data to tell us when transformers will fail. Beyond space weather, transformers can fail for a number of reasons, including most importantly their service and maintenance histories. However, given the diversity and breadth of the analytical results noted here, the NERC standards drafting process set the 75 ampere limit as a conservative floor below which the transformer owners need not be concerned about overheating for the benchmark event.
Contrary to Mr. Harris’ claims, the standards drafting process neither encourages nor discourages the use of transformer GIC blocking devices as a means of GMD mitigation. Such devices hold potential for future use and early results from the first field deployed unit have been positive. However, such devices are one of many strategies that system operators and planners may need to deploy to address the potential impacts of severe space weather. The purpose of the NERC standard is to put the analytical processes in place to figure out how to best protect the North American power system from severe space weather.