I like your thinking :angel:1 second will work from here.
15, 20 and 30 amp branch circuits. At 120 volts to ground the breaker is required to trip at 0.8 seconds or under. At 150 volts to ground 0.4 seconds or under. Sounds like a lot simply going from single phase to three phase.What are you removing power from? Is there a current level and time at 150 volts?
I know it’s all above my pay scale, but I’m curious what you are attempting to do.
If you know the short circuit current at 150V, the short circuit rating constant ( K ) of the type of cable, obtainable from cable manufacturers, then you can calculate the area of cable suitable for your requirement. The formula is . Area= (I/K)*√time. Note:The formula applicable upto 5 seconds only.Is there any real danger in using a 0.8 seconds as disconnection time for 150 volts line to ground? Or would a sweet spot at 0.7 seconds work? Call me cheap but I don't want to use 0.4 seconds unless I really have to.
Sahib, this is what I'm looking for! I have the mm2. Is this enough?Ah! The area as expressed in formula in my previous post is in Sq.mm.
I can recall an old farmhouse way out , with a barn wired off of it, to yet another barn in the back 40....
One could arc something all day long, w/out the ocpd opening @ the main house
~RJ~
Yup! You see what I'm trying to avoid (trying to accomplish)A LONG time ago I did an absolute Minimum with max VD for a short time project. 240v 3Ph, IIRC. Under a bolted fault that developed at the far end, the voltage would drop out the control but never blew a 60 amp fuse.
Perhaps this would help:Yup! You see what I'm trying to avoid (trying to accomplish)
So how do I go about the math? :dunce:
Enough for what?Sahib, this is what I'm looking for! I have the mm2. Is this enough?
For the area of the cable.Enough for what?
I personally never did.For the area of the cable.
Do you do loop impedance in your Country?
Have you ever done the calcs? I'm curious how 1.5, 2.5 and 4mm2 cable will behave.I personally never did.
No occasion arose for me to do the calculation because I need only to apply ready made schedule of work for standard electrical works in telephone exchange buildings. But in your case to do the calculation, you need to know also the prospective short circuit current as well as the constant k. Also see the websites mentioned in synchro last post for clarity.Have you ever done the calcs? I'm curious how 1.5, 2.5 and 4mm2 cable will behave.
Say I have a 750 kva 5% Z 138/240Y transformer.No occasion arose for me to do the calculation because I need only to apply ready made schedule of work for standard electrical works in telephone exchange buildings. But in your case to do the calculation, you need to know also the prospective short circuit current as well as the constant k. Also see the websites mentioned in synchro last post for clarity.