I assume the formula to get X'd from x'd is the same as X"d?

In the short circuit current equation for the variable Isc3, what does the 3 signify?

Brought to you by Schneider Electric

I assume the formula to get X'd from x'd is the same as X"d?

In the short circuit current equation for the variable Isc3, what does the 3 signify?

Yes, the formula to get $X_{d}^{'}$ from $x_{d}^{'}$ is the same as for $X_{d}^{''}$ .

To be transparent, I need to check with our experts:

- to confirm what I think = that I
_{cc3}is the short-circuit current for a three line short circuit - to confirm if this paragraph is still up-to-date (it was not reviewed for some time)

Hi @DMullins in fact on the right of the equation you have $x_{d}^{''}$
, expressed in %, which is a characteristic of the generator during subtransient phase (= subtransient reactance, expressed in %, only the reactance is used because the resistance is negligible). This characteristic is provided by the manufacturer (see **Fig.N5** for an example of manufacturer impedance table in %). It is used in the equation to calculate $X_{d}^{''}$
, which is the generator actual short-circuit impedance (in ohms) during subtransient phase. **Does that clarify it?**

I also made small modifications to this paragraph (fine-tuned the look&feel of the equation, used an inline equation for $x_{d}^{''}$ for coherence, I hope it helps making things more clear

There are no older topics

The Electrical Installation Guide is now available here as a wiki (Electrical Installation Wiki). This wiki is a collaborative platform, brought to you by Schneider Electric: our experts are continuously improving its content, as they were doing for the guide. Collaboration to this wiki is also open to all.