Hello. I was recently told by a colleague in Europe that transformer manufacturers in Europe are not recommending ester oils, either natural or synthetic, on new units. Supposedly, there are some issues people are seeing. This seems a little different than I have heard. Are there long term...
I have seen this design in smaller, utility style pad mounted transformers, but in general, we don't see them in substation transformers. In what applications are these used in your country? Industrial plants tend to be a bit more conservative in nature and not use "new" designs, so there is...
Bill, thank you for the response. I don't think I am concerned about mitigating the first factor, as the duration should not cause any problems. Is there a significant duration to the second component?
We are looking at installing an induction generator into an industrial facility. A question has come up to the inrush of the machine if it is accelerated to synchronous speed by the prime mover before the generator breaker is closed. In my mind, this is essentially the same thing as energizing...
How compatible is equipment with Class 1 Div 2 rating with a Class 1 Zone 2 area in North America? Some of the equipment we are trying to use only has the Div rating, and not the zone.
My personal preference is to make e-stop circuits as simple as possible. I want to know they are going to work when needed. Your original approach will work, but look at the number of devices you are adding to this system with a controller and additional interposing relays. On the larger...
I found the sample questions booklet offered on the NCEES web site to be about the best reference, other than the NEC Handbook. I found the questions to be similar to the ones on the test. I alsot used the Power Reference Manual by Camara and the Kaplan Power PE study guide (which turns out...
How high were the fault levels? One of the issues we have had at our facility is increased available fault current has made some of the older stations buss diff settings/CT ratings susceptible to CT saturation, much like what isquaredr is saying.
I think it is more proper to say the grounding resistor allows a maximum of 400A of ground current to flow. Any impedance in the fault will lower the current to some level below 400A.
Rockman, your basic approach sounds like it is on track. I would say that in general, you need to make sure...
Basler has a spreadsheet on their website that can be used to predict operate and restraint currents using measured CT currents. You might consider downloading and running it using measured CT secondary values.
Have you performed a load check on the secondary CT wiring to confirm expected inputs into the relay against a known quantity? We had two Basler 87T relays that operated fine with no trips for 3 or 4 years on two 35 MVA 69/13.8 kV transformers on a M-T-M substation. Then 2010, we had the...
The bus bracing is 40kA and the interrupting rating on the breakers is also 40 kA. My concern is on the breakers. We are hearing the older versions of the ANSI standards allowed for a higher interrupting rating on breakers for SLG faults over 3PH, but we are pulling the newer standard to see...
