Consideration of Comments on Draft Standard MOD-026-1 for the Generator Verification Standard Drafting Team — Project 2007-09 The Generator Verification Standard Drafting Team (SDT) thanks all responders submitting comments on the proposed revision to the MOD-026-1 — Verification of Models and Data for Generator Excitation System Functions standard. This standard was posted for a 45-day public comment period from February 17, 2009 through April 2, 2009. The stakeholders were asked to provide feedback on the standards through a special Electronic Comment Form. There were 45 sets of comments, including comments from more than 100 different people from over 50 companies representing 8 of the 10 Industry Segments as shown in the Attachment on the following pages. http://www.nerc.com/filez/standards/Generator-Verification-Project-2007- 09.html In the formation of the first draft of this excitation control system model verification standard, the SDT first considered the functional entity “applicability”. The SDT quickly recognized that assigning responsibility to appropriate entities for a continent-wide standard on verifying unit excitation system models would be difficult. The reason is that there are many business model variations regarding excitation model verification in place today. The SDT decided that a generation entity was the appropriate entity to assign ultimate responsibility, and posed this question to industry. The vast majority of respondents did not think the Transmission Planning entity was the correct entity to perform verification. There was a significant portion of industry that thought the Generator Owner should be responsible instead of the Generator Operator. The SDT consulted the Functional Model Working Group (FMWG), who rendered the opinion that the Generator Owner should be responsible for model verification, not the Generator Operator. Based on consultation with the FMWG, and supported by the majority of industry comments, the SDT has changed the applicability from the Generator Operator to the Generator Owner. The SDT asked the industry several questions regarding applicability and frequency of excitation control system model verification. The industry responded that the proposed ten-year periodicity, the proxy unit concept, exemption for units that have a 5% or less capacity factor, and an applicability on an Interconnection basis corresponding to at least an 80% installed MVA generation capacity are all acceptable. Based on industry comments, the SDT is proposing that the proxy unit cutoff be raised from 250 MVA to 350 MVA (the other criteria remaining unchanged). Also based on industry responses, the SDT is proposing a modified applicability to additionally include a significant MVA percentage of all generation of all technologies, including Variable Energy Resources. The SDT also asked industry about the role of generator model data, because the excitation control system model is a closed loop system that includes the generator data. Industry stakeholders indicated that the standard needed additional clarity about the exact expectations for generator data, but indicated that expanding the scope of the standard to include verification of generator models was not appropriate. There was support for the SDT approach of the standard “stating what is required” without “stating how to accomplish what is required”. Specifically, the industry agreed that the generation entity (the Generator Owner) should be tasked with determining if the model’s predicted response and the actual equipment’s recorded response are sufficiently matched, and with the concept of the standard providing minimal specificity regarding the mechanics of performing excitation system verification.
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