Search results for query: *

Hi - You can't do a grounding study without a drawing of a ground grid - Every ground grid can be different. You need to at least get a drawing of the station area from the customer, including everything to be within and adjacent to the ground grid area, then lay out a ground grid, then take...

We protect our feeders with a three phase overcurrent pickup of 720A. Our feeder equipment rating is 600A. Our station breakers may have a higher rating but I'm not sure. For feeders like this, we have 24 hour control room monitoring so if the load approaches 5 or 600 A then we would off load...

Thank you all for the responses. Stevenal - thanks for the info on coordination - this is how I would have thought to approach a system with multiple transformers instead of adding up the total kVA connected and treating this as one large transformer and trying to assume a total inrush amount...

thanks tinfoil. jghirst - I don't have any references that relate inrush to total impedance. I've used past practice of 10 x full load current for 0.1 sec. to calculate inrush current. Impedances are typically 4.5 % for the 1 MVA transformers and 5-10 % for the 10 MVA transformer from my...

HI - We have a customer with 10, 1 MVA transformers connected to our utility system at 13.8 kV three phase. Our current practice for fuse sizing is to assume that the inrush current would be the same as for 1 - 10 MVA transformer. Does anyone know if the total inrush for multiple transformers...

Our standard cable is concentric neutral. Sometimes we use the neutral for unbalance current and sometimes we open it at one end to increase the ampacity but this always involves us having to install a separate neutral conductor. I haven't seen this configuration we've found with both ends of...

Hi, We've found a relatively new cable installation where 2 underground feeders have been installed to service an industrial park. The cable is 750MCM Cu, 28kV concentric neutral, 3 conductors per circuit. The system voltage is 27.6kV. A separate 350 MCM Cu neutral has been installed and...

Thank you for the posts. I agree that equipotential grounding is what should have been done. More of a personal interest after the fact thing for me to want to calculate and measure the effects of the induction that occurred. Veman.

Thanks very much for the quick responses. About the equipotential grounding, the wire was coiled at the base of the pole and when our guy grabbed it, it was energized with induction so, because the guy was on the ground, I'm not sure how equipotential grounding could have been applied. The...

Hi, We had an incident where a lineman was installing a new line across a road. There are two parallel circuits with one disconnected and grounded at one end. There was a high voltage measured at the other end of the disconnected line. Does anyone know where I might find information on how...

Thanks for the replies - I have read that it does occur in Y-Y transformers because of lower loss cores that have been used in recent years. The reason for my question is there is no 3 phase switch in the supply right now and I am debating spending the extra $ on installing one so it looks like...

Thanks for the replies... (still looking though)

I use the calculator on www.arcadvisor.com for low voltage/switchgear calcs and the duke power utility program for MV line calcs (see attached). http://files.engineering.com/getfile.aspx?folder=872a990d-857d-456a-ac5d-e7d6e6ee6b7d&file=FLUX.EXE

We have a 1200' run of 13.8 kV underground cable feeding a 3 phase padmounted 500 kVA Yg-Yg transformer from 3 single phase fuses. I have found some new information on ferroresonance that suggests that there still may be ferroresonace occuring in the YY transformer because of the newer low loss...