I used one like that to field calculate the impedance of a very large transformer (138kV, 100 MVA or so). I was impressed with myself that I came up with the same numbers as they did in the factory, it does have it's uses.
The controls had some issues with cycling the cap bank, that likely caused the trip, also could be harmonics on energizing. That's separate issues which will get resolved. In this case it's in relatively steady states for pre and post faults.
My question is much more basic. This isn't...
The fuses that blew were the A phase fuses, which caused a neutral over voltage, sensed by the SEL 487v, causing CS35-1 to open. I added a 3 line to the attachment with notes. https://files.engineering.com/getfile.aspx?folder=209d263e-f09a-44a9-90fa-7210ac625728&file=Cap_A_fuses_trip_Fox_SQ_2.pdf
This is a ungrounded neutral capacitor bank tied to a 34.5kV main power transformer Y grounded. All the A phase fuses blew, not sure why currently. I'm looking at the event and the neutral voltage before the event was 1.2 kV < -178, likely due to voltage imbalance. After the event, before it...
The only time I have had one of them smoke was when there was a standing trip and the handle was held closed. The coils are good for about 20 seconds with full voltage before the smoke comes out. I have seen them fail because of operator holding the handle, which ends up fixing the problem for...
Use 2 wires into each rtd, if it's a short run it will be less than an ohm, you could measure the lead resistance and determine a fudge factor for error and adjust trips accordingly. At least it's not a 10 ohm rtd, which would add errors faster. David
Usually RTDs are 3 wire, 2 for detection of wire resistance, and the 3rd for the RTD. First check the manual to see how it should be wired. The shield is usually separate and grounded at kne end only, if 3 wire, use 3 wires.
David
The attached file isn't valid, comtrade files require *.CFG and *.DAT files to open.
It's hard to judge settings without knowing the CT ratio, but a good guess is 240/1 (1200/5). If that is true then the time over current setting setting is 1056 amps (1.8xFLA) and the Inst 2 over current is...
What are the best practices for settings the fan control temperatures on a 50-100 MVA, 65C rise, ONAN/ONAF/ONAF, mineral oil transformer? What temperatures should the fans be set to operate at?
Usually I have seen 65C/75C or 75C/85C. We are in process of startup and the manufacture is...
It's just a single feeder with 10 padmounts in parallel. (the series comment was a brain fart, fixed) The first padmount blew up internally, no sign of damage from the outside, we found it by a resistance check from H1A-H1B, H2A-H2B (Both were open) and H3A-H3B (shorted). H1A is incoming from...
This is at a wind farm site where the cables are underground going to multiple padmounts connected in parallel, standard setup. The main power transformer is Wye connected on the 34.5kV side. The collector string is connected delta-Wye. We had a padmount nearest to the substation (connected...
This is what was installed in 2005 and operating currently. The site currently has a reoccurring ground fault (monthly??) that goes away without being able to find the ground fault. The site does trip off on ground fault (generator and utility). I'm wondering if the PT's can withstand full...
If I wanted to check the burden, I just powered it up with a relay test set and measured it with an ammeter, same with the CT, push 5 amps and measure the voltage. Usually not that much of an issue with the newer relays.
