Recent content by HYDL

We recently installed a new Asco closed transition ATS to feed a new data center at a hospital. To test the system, the electrician shut off the utility breaker feeding the transfer switch and the generator started up and the ATS transferred to emergency power. After the test was over, the...

I think what they may have going on is a high soil resistivity problem. Do you have any experience with a high soil resistivity and what occurs. I have the lightning protection folks checking that the bonding of the electrodes is complete.

Sorry if the info seems irrelevant....I tried to post what the contractor in the field reported to me. We did the lighting and power system engineering design for the building. The contractor is now installing what we designed....ie lighting, power, special systems. This voltage issue came up...

We have a project at Yellowstone National Park and the contactor is experiencing a voltage potential issue. It started with a 5 volt potential between metal steps, in contact with the ground and the various job trailers. They turned the power off at the meter pedestal, which disconnected all the...

This is a 1200 amp emergency feeder at a Hospital. EGC has 1.9 to 4.8 amps and max of 12 amps of leakage current.

Is there a standard that dictates how much equipment ground current is too much? Certainly, the ideal is zero, but what would be considered an acceptable level?

I am looking for information on how the NEC 250.66 table was derived for sizing the grounding electrode.

Any more thoughts on the derivation of the point-by-point formulas?

Thanks for all the input. Very helpful.

I am trying to learn what I can about Motor Whining. We have a cooling tower motor at our building that has a significant Whine. It is served by a VFD and I'm thinking that this may be the reason. Anyone have any input in this regard?

Thanks for responding. I understand the M being a percentage of available fault. What I'm trying to do is disect these formulas to determine how they were derived. All items in the f formula I can account for, but I'm not sure why they add 1 to the f and then take the inverse.

I've been evaluating the Point by Point method of AIC calcs that is in the Bussman Fuse book and also indicate in other literature. They have calculation for an f factor and an M factor. I'm trying to figure out where they come up with the M factor (the multiplying factor) 1/1+f.

Thanks all for the good information. I couldn't think of any reason to go Wye Wye. The system will not be paralleled with the utility. I'm finding out that they actually want this to be a portable setup on a trailer or two.

I 3 paralled Generators to power an Industrial System Wye System. This is a prime power application. The Generators will serve a Transformer that is 480v - 4160v Wye. The plant is mostly motor loads and will likely have some harmonics due to VFDs. I'm wondering if I should go with a Delta at...

I've been monitoring Harmonics at a 911 call center. They have two 12.5 KVA, 1-phase UPS at 240 volt. The 208 volt system has a boost transformer for each for the 240 volt. I've review the IEEE 519-1992 document. 3.5% is the highest THD that I've measure at the line side of the system. So...