Recent content by cbark

So what you are saying is that if the system ground is established at the switchgear, I don't need the bonding conductors from the transformer to the switchgear (only the phase and neutral conductors need to be installed from transformer to switchgear)? I assumed that they would still be needed...

We are installing a new 2500 kVA, 13,800-480Y/277 V transformer (solidly grounded) that will feed a new 480 V, 3000 A lineup of switchgear (3 phase, 4 wire). The transformer is located outside the building and will be cable connected to the new switchgear inside the building via underground...

We are adding a 2.5 MVA, 4.16 kV generator to an existing system. The 4.16 kV system is fed from a 12.47 kV-4.16 kV, 5 MVA transformer with a 400 A neutral grounding resistor. How should the generator neutral be grounded (high resistance, low resistance, etc.)? What IEEE standards would apply...

Why is it usually recommended to install an ungrounded cap bank on a resistance grounded system?

I have a question about how much current would flow for a ground fault on an ungrounded capacitor bank. The cap bank is a 12.47 kV, 1800 kVAR and it is being fed from a transformer with a 1000 A neutral grounding resistor. If one of the capacitors internally faulted to ground, how much ground...

Thanks for the valuable information in all of the posts, but my main question was the allowable voltage dip on the bus. From what I've read on several posts here, it looks like it really depends on what is on the bus and, in this case, there are only motors. I don't have the data sheets on...

We have a 4.16 kV MCC fed from a 5 MVA, 5.6% impedance transformer. There are several motors on this MCC and we are looking to add a new motor of undetermined size. I understand the voltage dip requirements for the new motor, but my question is what is the allowable voltage dip on the 4.16 kV...

Thank you sibeen and 7anoter4. I worked on this over the weekend and I got the same numbers. Thank you for the help.

Dy1

That's what I am having problems with. I know that the primary currents should be the secondary currents through the transformer ratio, but I can't figure out the vectors. I want to go through the numbers so that I can also look at other faults and determine what the currents should be.

We had a fault on a feeder off the the secondary of a Delta-Wye transformer that caused the primary overcurrent relays to operate. The relays that operated on the primary are electromechanical relays, so they don't provide any indication as to the fault current values. The secondary relays are...