Our city skyline is getting taller. So much so that the new taller high-rises are limited by voltage drop. We are having this issue on our Network system, where we typically service customers from the ground floor with either 480V or 208V. We considered running primary up the building and...
We have some 2-bushing 277/480V overhead transformers in stock and would like to use them to install a 480V open delta bank (versus using 3-bushing transformers that have a center tap, which we don't have in stock). I'm not a transformer connection expert, but I'm thinking I can delta-connect...
My utility started using a #2 Stranded Copper for their loop ground on overhead distribution transformers (versus #6 solid copper previously). I can't figure out the reasoning to this. For a 167kVA 120V transformer the fault current is max 57,300 amps. With this size fault current the...
In trying to determing the ratings of underground cable for my company I determined that the manufacturers vary widely in their ratings, i.e., for 25kV 4/0 Copper 1/3 neutral 260 Mil insulated cable buried in ducts: Southwire = 287 Amps, King Wire = 320 Amps, and Perreli = 314 Amps. The ratings...
I've heard talk that pulling urd cable into metal conduit with one phase per conduit is a bad idea due to induction. We currently do so at our risers and then the cable runs into pvc conduit underground.
Does anyone know where I can find documentation on this subject or can explain to me the...
I work for a electrical distribution utility. This past season we have had over a dozen transformers that were struck by lightning, resulting in the transformer spliting from the top of the transforer close to the primary bushing and down to the tap changer (we use dual voltage 7.2kV/14.4kV...
I submitted this post in "Electric Motors & Controlls" but wanted to make sure I submitted it in the right catagory.
I work for a utility company and a customer of ours requested a 3-phase padmount 480V delta transformer to connect a 3-phase 480V pump motor. These are rare and it is...
I'm looking for some data on determining when pulling rope burns though PVC conduit elbows in order to determine when to use rigid metal conduit elbows. My electric coop currently requires the use of rigid metal elbows for pulls over 250 feet. I would like to see data to support this. It's my...
Is there any negative results to leaving out the neutral in a 277/480V 3-Ph Y-Y padmount transformer to only utilize the 480V?
Occasionally our customers request this. The only negative aspect I can see is that a fault may cause an imbalance and may not be sensed by the current limiting fuse.
Can anyone give me an idea on how to calculate voltage drop through a transformer due to load?
Our system is 12470/7200 primary. For example I want to calculate the voltage drop through a 25 kVA 120/240 padmount transformer with a 4kVA load. The %Z on the nameplate is 1.9 and the R/X ratio is...
