Talk:Short circuit ratio

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Electrical engineering

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Definition is very confusing and contradictory[edit]

The second sentence reads It is the ratio of field current required to produce rated armature voltage at the open circuit to the field current required to produce the rated armature current at short circuit, this text (not the definition!) only makes sense for a single synchronous generator. Immediately the third sentence talks about can be calculated for each point on a grid. But the grid as a whole does not have "armature" (neither does any inverter-based resource). In my opinion, definition need to be re-done in more generic terms (ratio of short-circuit power to the nameplate capacity, see [1] p. 39) that is suitable for the grid. Even then it cannot be calculated at an arbitrary point in the grid, a "point of interconnection" (POI) needs to be introduced. See some discussion at [2]. I am planning to change the lead to more conventional definition and, prior to that, soliciting the comments hereby. Викидим (talk) 22:36, 11 June 2023 (UTC)[reply]

For the synchronous machine, the definition in the current lead can be sourced from the second source provided, see the quoted p. 740 ([3]). However, the formula is immediately simplified there (12.6) to an inverse of the per-unit synchronous reactance (the "direct-axis" component, X_d). While some relationship between these definitions does exist, the values for the grid and for the generator (as currently defined) are quite different. Generator with an SCR of 0.9 is quite "stiff" (there are reasons not to go this high); the grid for stability needs more than 1 (typically a value above 5 of a differently defined SCR, see the section 10.6 of the Kundur's book I have added to the Sources section of the article, electronic copies of this book are widely available). I am still looking for a single source that clearly separates what looks like two different SCRs. This article might need to be split - also soliciting the comments. Викидим (talk) 23:24, 11 June 2023 (UTC)[reply]

Perhaps, we can split by creating a new article for Grid strength, of which the SCR (of the grid variety) is a measure, see the cited Kundur book. Викидим (talk) 15:42, 12 June 2023 (UTC)[reply]

See also the source [4] with high value of SCR for generators (page 3-3) implying yet another aspect (the definition on p. 3-2 is conventional). It seems that the Corps got the numbers upside-down, a nice treatment at [5] confirms my recollections: as defined (d/h on horizontal axis in Fig. 7-22), the SCR for the synchronous machine with cylindrical rotor is below 1 (the machines with salient pole rotors are in 1.0-1.5 range). Викидим (talk) 16:17, 12 June 2023 (UTC)[reply]

Found a source that clearly spells the difference, although quite low in authority [6], three (!) different definition of SCR. I therefore propose to (1) split the current article in two:Short circuit ratio (synchronous generator) + Short circuit ratio (electrical grid), (2) convert the Short circuit ratio into a WP:Disambiguation with all three options (one without an article). Once again looking for comments. Викидим (talk) 07:21, 15 June 2023 (UTC)[reply]

No objections for two weeks. I will start WP:CONSPLIT. Викидим (talk) 06:30, 29 June 2023 (UTC)[reply]

See also IEEE Standard 519-2014, as well as some discussion (on the grid variety) at [7]. Викидим (talk) 15:51, 12 June 2023 (UTC)[reply]

The issue with inverter-based resources in weak grids is described in a simple form in [8]. Викидим (talk) 15:57, 12 June 2023 (UTC)[reply]

WP:CONSPLIT Done --Викидим (talk) 16:53, 30 June 2023 (UTC)[reply]

System condition rating[edit]

Our article lists some values for "system condition rating", also an SCR. This appears to be a typo. Викидим (talk) 23:31, 11 June 2023 (UTC)[reply]