I am wondering if anybody is up on IEEE standards. We have found a that IEEE 422 was rescinded sometime around 1994. We have an engineering firm that is adamant that signal cables are required to be run in Rigid conduit when routing through underground duct banks in a power plant per the 422...
You didn't specify weather you are using multi conductor tray cable or single conductor cables grouped. If single conductor, yes. If its tray cable you size per B.310.3 in Annex B.
OK I think we got it. We had the T60 Guru from GE out today and it was a combination of many of the suggestions above. On two of the transformers, the 1500KVA, the drawings were wrong and the phase shift was wrong. We swapped some CT leads at the test block to push secondary current through the...
I have a little more info. We changed the tap and programing on the 2500KVA transformer to 300:5 and were able to bring the load (480 side) up to about 350A with no trips. We were able to look at the vector diagrams in the T60 software and an interesting thing was happening. The primary and...
The CT ratios match the ones programed in the relays. We confirmed that last Friday. Though we did find that the 2500KVA transformer was set at 300:5 in the relay (where it should be) and the CT's are tapped at 100:5. The relay was changed to mach the tap at 100:5 which is different than it's A...
I am dealing with a nuisance tripping problem on a differential protection scheme and am looking for some help in understanding as this is a bit over my head. (We do have an engineer working on the problem as well)
The situation is we have a line up of GE 15KV switchgear with A and B side feeds...
Update:
I received an email today that the problem is resolved. Apparently there was a technician from the generator manufacturer out last week. Why it took the generator supplier 18 months to make this happen is unknown to me. In his report he states he found the neutral current trip "set...
Thank you for the replies. So if it is third harmonic current putting the relay over the threshold, we should be able to measure the neutral current with a regular amp meter and a true RMS amp meter and verify this right? We are scheduling one of or service people to go up and take a bunch of...
A year an a half ago I installed a cogeneration plant at a hospital. The scope involved combining three separate services into one 4000A 277/480V service and all work associated with a 600KW 277/480V 4W generator that parallels with the local utility. There is a heat exchanger that heats a...
I have a book but unfortunately I don't think you can buy it. It is a special publishing by the NJATC.
I can hand tape. I keep the skills up even though I don't do it often. Some places still demand hand tapped splices and terminations. When done right they will out last the kits. A high...
I don't have any new info other than some voltage and current readings the operators recorded. The internal short to ground is an interesting point. During the commissioning process the generator controls start up man closed the breaker 180 deg out of sinc. The generator just about lifted off...
Hello,
A job I did last year suddenly started having problems. It is a 600KW Co Generation unit at a hospital. The operating voltage is 480V. Everything worked fine for months and now it seems to be tripping on a "Neutral Current Fault". I don't have any more detail as I haven't been back to...
Thank you for all the input. It's much appreciated. BTW-The power cable is EPR with a copper tape shields, not concentric neutral. I agree with not relying on the tank for a ground path. Also, most manufacturer literature I have read suggests using skirted terminations in outdoor gear even if it...
I am looking for some input on these pictures. http://www.electrical-contractor.net/Forum/Images/SurgeArrestor-1.jpg
http://www.electrical-contractor.net/Forum/Images/SurgeArrestor-2.jpg
This is the 12KV secondary of one of two step up transformers on a rush project. I did the terminations...
Wow, thanks for the replies. I guess it will work but based on what everyone has said I think I will just get the PT's like the generator manufacturer wants. If we did use the wye connected PT's and something did go wrong I'm sure it would be our fault. A couple hundred bucks for PT's is cheap...
I have an issue on a co-gen project where the controls on the generator are expecting to see open delta connected PT's (480 to 120V) on each side of the generator breaker for synchronizing to the utility. The controls in the switch gear, where we will be pulling the signal from, have this set up...
