PracticalQuixotism
Electrical
- Dec 2, 2009
- 2
For a DC fault involving multiple current sources and a common branch, equation 50 of IEC 61660-1 describes a correction factor to be used in determining the short circuit current delivered by a source to the fault location. For source j, the correction factor is given as
?_j = R_resj * (R_ij + R_Y) / (R_resj*R_ij + R_ij*R_Y + R_resj*R_Y),
where R_resj is the equivalent resistance of the other parallel source branches that contribute to the short circuit current through the common branch; R_ij is the resistance of the source up to the common branch; and R_Y is the resistance of the common branch.
In my case, I'm analyzing a system consisting of a battery and a battery charger delivering short circuit current through a common branch. Using the above equation, the correction factor for the battery charger would be
? = R_bat * (R_chg + R_Y) / (R_bat*R_chg + R_chg*R_Y + R_bat*R_Y),
where R_bat is the resistance of the battery circuit up to the common branch, and R_chg is the resistance of the battery charger circuit up to the common branch.
Before considering the IEC 61660-1 correction factor, I had been planning to correct the battery charger current using the following equation:
? = R_bat / (R_bat + R_Y),
which simply describes how much of the battery charger current flows to though the common branch to the fault as opposed to flowing towards the battery.
I am interested in determining why these two equations are different. Am I blatantly misinterpreting something, or does the IEC equation take into account addition factors that I am not considering? I was wondering if someone could explain how the IEC 61660-1 correction factor is derived or otherwise direct me to a helpful reference.
?_j = R_resj * (R_ij + R_Y) / (R_resj*R_ij + R_ij*R_Y + R_resj*R_Y),
where R_resj is the equivalent resistance of the other parallel source branches that contribute to the short circuit current through the common branch; R_ij is the resistance of the source up to the common branch; and R_Y is the resistance of the common branch.
In my case, I'm analyzing a system consisting of a battery and a battery charger delivering short circuit current through a common branch. Using the above equation, the correction factor for the battery charger would be
? = R_bat * (R_chg + R_Y) / (R_bat*R_chg + R_chg*R_Y + R_bat*R_Y),
where R_bat is the resistance of the battery circuit up to the common branch, and R_chg is the resistance of the battery charger circuit up to the common branch.
Before considering the IEC 61660-1 correction factor, I had been planning to correct the battery charger current using the following equation:
? = R_bat / (R_bat + R_Y),
which simply describes how much of the battery charger current flows to though the common branch to the fault as opposed to flowing towards the battery.
I am interested in determining why these two equations are different. Am I blatantly misinterpreting something, or does the IEC equation take into account addition factors that I am not considering? I was wondering if someone could explain how the IEC 61660-1 correction factor is derived or otherwise direct me to a helpful reference.