Recent content by daviandgo

This organization published a study on ferroresonance and cable lengths. http://www.dstar.org/research/project-desc/ferroresonance/.

Check with Coned in New York. In 2006 they experienced a significant outage in one of their networks. I recall reading that inrush caused some network feeder breakers to reopen. I do not know how detailed their post event analysis was and I do not have any contacts at Coned.

I am not aware of any undesirable activation. No time delay is used. Recall that this is to block transfer back to the utility. No change was made to the transfer from the utility in the event of a loss of voltage on one or more phases.

I am not aware on any

Here is some more information. Pad-Mounted Transformer 2500 kVA, 34.5kV YG/480V YG System Phase Rotation: CBA Measured Values: With all fuses in (Load on transformer) Negative-to-positive Ratio: 0.2% With C-phase fuse removed (No load on transformer) Negative-to-positive Ratio: 4.3% With B-phase...

We had a similar situation. The ATS manufacturer installed a Negative Sequence Voltage Detection Relay. The relay was programmed to prevent retransfer to utility if the negative to positive sequence voltage percentage was greater than 2%. This solved the problem.

"I have the curve from the manufacturers for one of the transformers. It indicates current decays from 1300A to 350 A in 0.5s. (Rated current 173A). There are four transformers in total. That means the current in the incomer goes from 5200A to 1400A in 0.5s)" I believe the simultaneous...

Alehman, thanks for your response. The most practical solution at this location is to add a "small" load to the transformer. Any guidance in estimating the "small" load? Thanks.

One of our customers is served from a 2500 kVA PMT, 5-legged, 35 kV Gnd Wye - 480V Gnd Wye. The 35 kV feed is from a fused Overhead lateral line to a fused terminal pole. The cable from the TP to the transformer is about 100' 1/0 AL EPR cable. The customer has a transfer switch that senses...

Thank you DPC. The ANSI C57 pad-mounted transformer standard does not refer to any thickness requirement. There are several other transformer related ANSI standards. These standards are not available to me at this time. Since the standards are relatively expensive I am hoping that someone...

Does any IEEE/ANSI transformer standard state the minimum thickness of a pad mounted transformer tank? Or is any thickness acceptable AS LONG AS the transformer tank meets the pressure withstand requirements?

MartinBEng, I am not sure but their web site lists devices with which their software has been used.

Hi MartinBEng If you want to monitor devices from other manufacrurers, you may want to look at http://www.autosoln.com. Automation Solutions has software that can communicate to many devices, including the IQ Analyzer. We have used it with CH's MPCV relay, IQ 200 meter, and Allen-Bradley...

No. All customers on our 35 kV system are fed radially.

Thanks for your response. The upstream device is the substation breaker. However, there are a few taps off the main circuit feeding fuse protected transformers.