Recent content by AggiesNM

So all this fuss to limit zero sequence currents from appearing on the high side? I feel we can live with this trade-off.(implement high-speed tripping, relocate comms to microwave or fiber to prevent interference et. al.)

I feel a delta-wye transformer just about complicates everything when it comes to high voltage substation design. Why aren't Y-grnd - Y-grnd the norm in the power system? Only at bulk power EHV do I see Y-Y. Why not in distribution, 138kV and down?

Hey guys we are putting in a battery energy storage device. Part of the system requires a backup power supply to black start the battery and tie it into the microgrid. The backup supply chosen is a UPS system. I am a substation engineer with no background in UPS system. I am given a bunch of...

I know there are other phase shifts possible. I was looking through the Basler paper on the phase shift. It is nice to see all combinations possible but the re-wiring was all done inside the transformer. I am still unable to process in my head, how rolling or flopping phases externally gets us...

Hey, In the attached picture, the 30degree phase shift transformer is shown. Now I would like to change this to a 330degree DYn11. How do I accomplish this using phase leads that are landing on the transformer bushing...

Noted. Thank you.

Hello fellow engineers, I need help with something basic. If the phasors are rotating ABC counterclockwise. Is it possible to change this to ACB through a transformer? In other words, can the phasor rotation be changed at the transformer? Thanks

I am a little bit confused now. I came across this GE publication that recommends sizing the arrester rating at 70% of line-to-line system operating voltage. I am thinking 24.4kV MCOV station class in the neutral.I have based this on the recommendation shown on page 16 (of 19) in the attached...

What is I in the I x drop across reactor? Continuous rating of the reactor?

Hi, I need to specify a surge arrester in the neutral circuit of a 99MVA 138kv-34.5kv (14.4kv tertiary) auto transformer. The arrester will be located in the neutral circuit of the secondary winding (34.5kV) and is placed between the transformer neutral and a neutral grounding reactor (1ohm...

@liteyear You are talking about high impedance reactor grounding (using a peterson coil). I would like to stick with the low impedance grounding scheme. I believe there are no complexities like matching reactance to distributed capacitance in this case. Also, the low side is connected to the...

@Marmite The GSU transformer is connected to the utility grid on the high side and to the wind turbines on the low side. There is no single phase load as far as I see. Are you concerned about the unbalanced loads? I see the benefit in sticking with a resistor. Regards.

@rcwilson, I believe I don't need to specify the zero sequence impedance of the transformer and the system to specify a reactor. The reactors impedance alone should limit the fault current to 600Amps. I guess that is what a manufacturer expects when I indicate that rating. However, getting...

Hi I've been working on a short circuit study for a collector substation for a wind farm site. I want to specify a neutral impedance in the secondary winding of the GSU auto-transformer which is rated at 99MVA (base @65C), 138kv-34.5kV (14.4kV tertiary). Some here prefer putting in a reactor...

My bad, I was referring to the conductor temperatures.