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Why you need to calculate? It is very strange to know why you cannot find the name plate of such a large critical transformer operating at 400kV?

CLEAN EARTH was an old idea when the manufacturers were not able to explain some erratic behavior of process control units. It is no longer valid now. Bond them together to make an equipotential. Also by separating them 5m in the soli do you think that it is possible to stop influencing the other?

I have no further comments until I see the transformer connections (vector group) at the other end of all feeders H01 to H06 feeders which I have already requested from newelecteng by my post on 28 Sep

1)Yes, you are correct. It is 2400V to ground. Therefore, no questions. You cannot use a 2400/4160Y PT on an impedance grounded system. Instead you have to use DUAL bushing, 5kV class, indoor or outdoor with a VTR=35 if your secondary system is 120V AC. Therefore, rated primary accuracy...

beyond86 Yes, but does it mean that the 33kV system has got 643A as charging current? How do you account for that? Before I make any further comments I am curious to know, 1) Is the 33kV system a real "DELTA" system? 2) Does the 33kV system really needs an earthing transformer? 3) If yes, how...

beyond86, Yes I noted it. See the feeder relay results. Io_calc =643.458(A) meaning 3I0=1929Amps is the earth fault current. How do you justify that amount of large earth fault current if the 33kV side is DELTA? If the 33kV system is really a DELTA bus then there is only the charging current...

newelecteng: I noted the following. From the incomer relay, I Found that U0=14407.808(V)=14.4kV Per your SLD the incomer is solidly grounded. Therefore,U0 cannot be 14.4kV. It should read 76kV. Per SLD there is no VT at the 132kV side. Any comments?

keeverw, Could you please upload the single line diagram? It should show the impedance data of the transformers.

newelecteng: Few questions to you please. 1)What is the reason for using WYE EARTHED transformer for the 132kV side? 2)Are all feeders H01 to H06 connected to generators exporting power to 132kV side or are they normal feeders connected to typical loads? 3)What is the vector group of the...

1) What is the earthing method of your 33kV system? 2) You have mentioned that an earthing transformer ZNyn1 is feeding your 400V system. Bit unusual for me. Could you please upload your SLD?

1) You are correct. The existing grounding transformer is directly connected to the existing 12.47kV distribution system. Per the given SLD, currently, the existing 12.47kV distribution system is ALREADY effectively grounded (Utility will not tolerate non-effectively grounded systems) and...

Can you please upload your SLD?

I donot know what you meant by frequency scan in insulation coordination study. Normally it is for harmonics. You can do the equivalent calculations of protective margins (PRL1, PRL2, PRS) for the surge arrester using a EMTP software. After modeling the substation at least for 5 spans, you allow...

Since your T2 is solidly grounded and single phase loads are served, any GF current will return back to the NEUTRAL of T2. Therefore, your 480V system fed by T2 is eff. grounded irrespective of T1 grounding method. If you perform a SC study you will find that COG of T2 system is less than 85%.

ETAP HELP is the best source to get a firm reply on how to model.

Interesting question. Could you please upload a sketch/ dwg showing the two grids and your concerns?

1) Is your 480V system is HRG or solidly grounded? 2) What is the Make & Model of the 400A fuse? 3) Could you please upload few photos?

Thanks Stevenal

I doubt whether you have expulsion fuses or current limiting fuses higher than 35kV.

1) Yes, pl. refer to the attached. 2) Yes, pl. refer to the attached...