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...
...of 400 you would get Zpu=100/400=.25pu.
I don't understand the math behind that simple formula as I would think the formula would be based on kV*kV/MVA. So with the utility at 69kV the Zbase would be69*69/100= 47.61 which would then be converted to Zpu somehow or other. I understand all...
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...
...60" pipe at the throat of the venturi. My job is to determine how much air is being injected and then the total flow. So assuming the entry is P1*A1 and the throat is P2*A2 and the water going into the venturi is at 30 psi at a velocity of 8.17 f/s in a 2" pipe I solved for P2. I came up...
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...
...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 = Va*sqr(3)with a positive 30 degree phase shift. Ia=Iab*sqr(3) with a negative 30 degree phase shift. You seem to be saying just the opposite in your...
...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 2160VA (4320*.5).
They then calculate the line current on phase A as:
The load on PP-1 is 3A phase-to-neutral (360/120). The load on PP-2,4 is 20.8A phase-to-phase...
