Recent content by bjenks

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.

Thank you everyone. Very good advice and points.

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...

Surely someone would look at this spreadsheet and comment back on the delta high leg phasor? Maybe people are worried about downloading stuff?

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...