lz5pl
Electrical
- Feb 6, 2007
- 313
I need to calculate short circuit current of a switchgear where co-generator unit will be connected in parallel with the grid. The specific point is that generator will be used at reduced power. Generator itself is 12 MVA, but the turbine will deliver only 8 MVA (limited by the available steam).
My question is: which value should I use for calculation of the reactance of the equivalent circuit - 12 MVA or 8 MVA.
According to me it should be 8 MVA, assuming that the generator will not be able to supply short circuit with energy equivalent to 12 MVA. But I am not absolutely sure, as my main field (control and relay protection) didn't help me to remember what exactly we studied 24 years ago in the University :~/.
Of course for dimensioning of switchgear panels I will use 12 MVA, but after adding the grid infeed we are going too close to the required 31.5 MVA (calculated is 30.9 MVA) and I just would like if we have some safety margin.
Any advice will be greatly appreciated!
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It may be like this in theory and practice, but in real life it is completely different.
The favourite sentence of my army sergeant
My question is: which value should I use for calculation of the reactance of the equivalent circuit - 12 MVA or 8 MVA.
According to me it should be 8 MVA, assuming that the generator will not be able to supply short circuit with energy equivalent to 12 MVA. But I am not absolutely sure, as my main field (control and relay protection) didn't help me to remember what exactly we studied 24 years ago in the University :~/.
Of course for dimensioning of switchgear panels I will use 12 MVA, but after adding the grid infeed we are going too close to the required 31.5 MVA (calculated is 30.9 MVA) and I just would like if we have some safety margin.
Any advice will be greatly appreciated!
------------------------
It may be like this in theory and practice, but in real life it is completely different.
The favourite sentence of my army sergeant