anybody out there saturating CT's from inside relay room? we have 600V AC CT cables and I was wondering how much cable insulation can take since Saturation tests go up to 1200V AC?
any comments?
Also dry type Tx can withstand higher overloads then oil imersed Tx. It is also less maintenance on dry type, no need for oil sampling, just need to vacuum-clean/blow the dust off of the dry Tx. Insulation class as I said is much higher for dry Tx.
Agree with Sslobodan.
It's just a matter of how you connect winding taps internally in the transformer. I believe in Europe it is common to have Dy5. Here in North America we usually have Dy1 or Dy11.
Jghrist:
thanks a lot.
So it is not that impedance will be apparent for the relay in the TS, but also overcurrent protection will be measuring apparent current which is less then the current that the same relay measures w/o the generation. Great !
Thanks guys.
To clarify:
Embeded generator is generator that normally work in parallel with the grid.
TS relay is Transformer Station relay, this is first upstream protection of the feeder with embeded generator
I ran some models with embeded generation on utility feeder and I found that SC level seen by the TS relay protection remained constant.
However I came across some papers that say relay will see SC current decrease with new generation connected downstream on the feeder. This doesn't make sense...
is it possible to have delta (or ungrounded wye)winding configuration on primary of the generator step up transformer (higher voltage side) that feeds 4 wire system?
I would think neutral is needed to feed 4 wire system (grounded or not, but neutral must be there? Am I right?
Even if this...
OK. Customer hired Consultant who came back to Utility to complain about voltage dips. We set recorder on line for a week and recorded cyclic dips in voltage, one in particular went all the way to zero and yet current did not rise. I wonder if this was some kind of resonance, but I am not sure...
I don't have details about customer load yet. I understand there is motor that may have capacitor start. My question is for inrush of the motor is 2nd harmonic dominant as for the power transformers? Also what harmonics would come from motor load, say there is no VFD?
is there rule of thumb what causes harmonics in the system. Customer has single phase 240V motor pump and there is a cyclic sag in voltage and spike in current. THD is very hifg in range of 120% PREDOMINATE 3RD AND 5TH HARMONIC
voltage is high enough that megger (5kV DC) test will not give you complete results for condition of insulation. DOBLE test is what you need. It applyes AC 10kV voltage across the arrestor and measures capacitance, dissipation factor, leakage current.
