Prospective Short Circuit Current & Phase Angle

BrianDug

Hey I'm hoping someone can help me on this as its difficult to find an answer. I have checked ESBN technical documents but have not found the information I'm looking for, perhaps I'l drop them an email if nobody can help.

Say for instance we are performing a short circuit study for an installation. We measure the earth fault loop impedance (Ze) from the consumer unit back through the DNO supply/supply transformer winding. And as an example say Ze = 0.0255 which would equate to Ipscc = 9000A @ 230V. What angle would this be at? I hear the figure of 0.2 (78.4630 degrees) been thrown around but I am looking for a definitive answer.

Reasoning is when converting from polar to rectangular coordinates Z <Q --> R +jXL you really need to to have the reactance value or phase angle to do a definitive Ipscc calculation when summing your R + jXL values or Z<Q values.

Cheers

2011

BrianDug wrote: »

Say for instance we are performing a short circuit study for an installation. We measure the earth fault loop impedance (Ze) from the consumer unit back through the DNO supply/supply transformer winding. And as an example say Ze = 0.0255 which would equate to Ipscc = 9000A @ 230V. What angle would this be at?

To know that you need the Ze angle.

Ipscc @ (insert angle) = V @ (insert angle)/ Ze @ (insert angle)

Reasoning is when converting from polar to rectangular coordinates Z <Q --> R +jXL you really need to to have the reactance value or phase angle to do a definitive Ipscc calculation when summing your R + jXL values or Z<Q values.

Yes, you need this if you eant the angle as well as the magnitude of the prosective short circuit current. The angle will normally be quite "severe" as the inductive componet will generally be quite high (due to the transformer windings).

BrianDug

Yeah man I dropped ESBN an email, hopefully they will give me some information.

Cheers