QB64PE at work

[bobalooie]

I'm an electrical power engineer by profession. Frequently I need to calculate the available short circuit current in a circuit (electrical code requirement). I have very fancy analysis programs to calculate fault currents in a large system (say an entire building), but occasionally I need to quickly calculate a short circuit current for a single circuit or a very small network.

There is a well-documented method to calculate a short circuit current from point A to point B. Doing the calculation by hand is a PITA. So I put together a utility to do the calculation with a form-style data entry to avoid having to refer to all those tables.

The method's conductor constants as published only work on 60 Hz power systems. The conductor constants are invalid on 50 Hz power systems because the overall impedances are different. I haven't located an equivalent set of tables for 50 Hz systems, but I would be surprised to find they don't exist somewhere.

I plan to extend this to allow me to retrieve results from other studies and create a network in one overall project.

Real life QB64PE paying me back for all that money I spent on it.

[PhilOfPerth]

Maybe I'm missing something, but I believe the reactance of a circuit, however complex the circuit,, is dependent ONLY on frequency and the inductance ( or capacitance) of its components (2*PI*F*L or 1/(2*PI*F*C). Without seeing your actual setup, I would have thought it should be just a matter of replacing the frequency component in the fomulas. Maybe it's differrent in large-scale systems?

[bobalooie]

Maybe I'm missing something, but I believe the reactance of a circuit, however complex the circuit,, is dependent ONLY on frequency and the inductance ( or capacitance) of its components (2*PI*F*L or 1/(2*PI*F*C). Without seeing your actual setup, I would have thought it should be just a matter of replacing the frequency component in the fomulas. Maybe it's differrent in large-scale systems?

You are mostly correct about the reactances; the equations also take into account the inductive effect of steel conduits on the reactances. But you must remember that the impedances have been calculated in this method for 60 Hz systems, so the equations are already normalized for 60 Hz AC. AC circuits can be a bear to calculate in situ (I'm also an amateur radio operator, so I am accustomed to working in the frequency domain), but when one is operating at one singular frequency it is a simple exercise to reduce the AC equations to simple algebraic equations. So, the C values I have for the conductors are all calculated for 60 Hz systems, which is in use in the entirety of North America. Canada utilizes some different voltages than the US (the highest Canadian low-voltage industrial system is 575Y/347V, while in the US the highest low-voltage system is 480Y/277V.) Working with a singular line frequency is the only thing that makes electrical power engineering tolerable, because all the pertinent equations can be reduced to simple equations.

The high-dollar five-figure analysis programs can work in any system, but spending $30k on software isn't always the most efficient way to get a quick answer.

[Pete]

Great, but can it fix my toaster? I'm stuck here eating raw bread, if not.

Pete  

- I likes my toast with butter and jam. I hates green eggs, Sam I am.

[bobalooie]

Great, but can it fix my toaster? I'm stuck here eating raw bread, if not.

Pete  

- I likes my toast with butter and jam. I hates green eggs, Sam I am.

Well, a strong enough short circuit will fix your toaster right good. And thoroughly toast whatever is in it.

[Pete]