I believe I am able to answer my own question for how Zpu= kVAbase/kVA:
1) Zpu= Z/Zbase
2) Z= V2/VA
3) Therefore Zpu= [V2/VA]/[Vbase2/VbaseAbase]
4) Since we are using the utility fault data, we are setting Vbase=V=VLL
5) Substituting into formula 3 we get Zpu= [V2/VA]/[V2/VbaseAbase]
6) The...
In the IEEE Red book, when you are calculating the utility Zpu they just use the simple formula: (KVAbase)/(KVAsource) which is a unit less number.
Thus for a base of 100MVA and a fault MVA of 400 you would get Zpu=100/400=.25pu.
I don't understand the math behind that simple formula as I would...
Thanks chicopee, I actually have the Marks Standard Handbook for ME and it does have the basic venturi info, but nothing on design of a system that consist of a incompressible fluid going through a venturi that then suck in air and pushes out a combined mixture. air lift pumps are based on...
I am trying to do some energy calculations for an aquaculture project that is trying to calculate different methods of creating flow in a channel and injecting air into water. So I am electrical engineer in background, but have some basic fluid knowledge. They currently want me to evaluate a 2...
Only through galvanic corrosion, which would require another metal close by for the aluminum to send ions too. Otherwise Aluminum Oxide is a great protector against corrosion. Especially, if a marine type alloy was used. Just learned this recently through exhaustive research.
480V system, there were parallel feeds (basically doubled the size needed) for voltage drop. Nobody know how much current was driven though it during the failure of the splices. However, full load is like 180A which is way below the rating of the parallel feeds.
Potteryshard, I am interested...
The cause of the water boiling was from them having a disconnect at the utility transformer and then running the 1000 ft service lateral out to the marsh area where the pumps are located (underground). When the splices got wet from ground water getting in the hand hole there was nothing there...
An electrician ran 1000 ft of parallel 350 kcmil Aluminum XLPE cables in a PVC conduit underground. The run was from a non-fused disconnect to several large brine pumps on a platform. About 500 ft in to the run they put a non-wet proof splice kit in. About 7 months ago the customer noticed...
Hi,
Awhile back I created a spreadsheet that showed how the current and voltage will change on a wye unbalanced system depending on single phase or three phase loads being added.
I have since tried doing the same thing with a delta high leg transformer. I can't find any real examples on the...
I should have mentioned that meggar does insulation test, but you can also do use a digital meggar ground resistance tester to determine the impedance of the copper too.
I do meggar test all the time to determine if cable are bad or not. Make sure you consider the length of the cable when doing the test and that you isolate both ends.
You are correct, I should have added that to make this complete. If I remember correctly, Leading PF would add to the original angle and Lagging would subtract. With that in mind I added this feature to the...
I started from scratch on the spreadsheet as I found two other errors. 1) I believe you have to replace PF angle from the actual angle. The orginal was just the opposite. 2) The Current nodes were in the wrong direction compared to the Voltage.
After fixing that, I was able to update the...
Found another error on the spreadsheet. Phase C had Ib instead of Ic in the formula. Please look this over and see if you see an error. Notice that adding a load to phase-N causes the current to go...
This a side notice, but without the single phase load the line current was 20.8A on A & B. Then you add an additional 3A on phase A and now your line current went down to 18.22 and 20.77A respectively. From a simple electric meter standpoint it looks like you are using less power even though...
everyone, I think we got it now. Thank you for your patients on helping me go over stuff I learned in college 25 years ago (although I sometimes wondered if I ever really did)... These software program are making it so we don't know if they are giving us the corrent information. This program...
I think we are now all on the same path now, thank you so much. Burn2x I see some things in your spreadsheet that don't make sense to me:
1) I think you are referencing to Vab, what confuses me is that I think I normally see Van as the reference.
2) I was under the impression that Vab =...
Just to clarify and for simplicity of the exercise:
This is a 208/120 V single phase panel (PP). Circuit PP-1 on phase A is a receptacle rated at 360VA. Circuit PP-2, PP-4 on phase A-B is two L-L loads that total 4320VA, but the panel schedule shows on Circuit PP-2 2160VA and Circuit PP-4...
