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In essence I’m trying to get the functionality of a DC-DC converter or simplified MPP circuit, but on a very small scale. The frequency is essentially DC. I’m looking to switch the load in milliseconds at worst. One-side grounded would work. I've done a lot of reading/searching. A...

My apologies for not defining the boundaries more clearly. The numbers cited were meant to indicate the approximate upper limits, and they don’t occur simultaneously. I’ll research the suggestons further. Thanks for the thoughts.

I'm trying to find something that would work as a voltage-controllable resistive load. I thought something simple might be available--where a DC control voltage could be used to yield a range of resistance values. Here are the basics: Resistance: span ~ 200-20,000 ohms. Sink capability: DC...

Never mind... I think I have it.. thx..

I understand how to translate positive sequence resistance values if they show up at a non-standard temperature on the test report. But what if this happens with the provided zero sequence T-model test data? Section 9.5.3 of IEEE Std C57.12.90-2006 references Z1, Z2, and Z3 as "Constants" in...

thank you both for your follow-ups...

Thx!!

Thx for the reply, dpc... That's not what I meant, 'tho. We do have calculations for the resistance... what I mean is, does the derating of the positive sequence values apply to the X or the Z. That is, should the equations instead be: 2-winding: X0 = X1 x 0.90 3-winding: XHL0 = 0.85 x XHL1...

We have formulas that estimate the zero-sequence impedance for CORE transformers based on the positive sequence values as follows: 2-winding: Z0 = Z1 x 0.90 3-winding: ZHL0 = 0.85 x ZHL1 ZHT0 = 0.75 x ZHT1 ZLT0 = 0.90 x ZLT1 Should it be the impedance that is...

Can anyone tell me why the above-mentioned standard goes through the trouble of defining the Protective Level "classification current" types in section 4.3.1, and then changes the terminology in section 5.4 to "coordinating current?" thx, john

Thanks for responding... In addition to the science, I guess I was particularly interested in how commonplace the use of arresters for this application might be at 69kV with ungrounded double wye banks. [It's kind of in the middle between typical higher voltage applications with grounded banks...

Can someone familiar with electric utility practices tell me whether surge arresters are typically used for Capacitor Bank switching applications--for 69kV ungrounded double "Y" banks? thx, - john

Thank you everyone for your input.... At the moment, I am reviewing IEEE C37.012. thx, - john

Do any of you regularly include shunt capacitor banks in your overall system models when performing short-circuit calculations/Breaker rating studies, or do you consider this a dynamic situation that is distinct from this process? - john

Thx!! - john

Hi... Can someone provide a technical distinction between a surge arrester and a surge suppressor? I believe they are both given under the umbrella term, "surge protective device"? thx, john

Ok, thanks for your help... - john

Thank you both for your replies... Ok, but can you be more specific when you say I need to "include a 0.975:1 (or 1:1.0256) transformer in the equations" when I parallel these transformers in my calculation? Let's say, for example, I have 4 transformers of this specification feeding a 13.8 kV...

Hi... We initially specified a 69/13.8 kV transformer with an impedance of .1942 p.u. (56 MVA, 69 kV). Then it was decided to specify the transformer with a high-side voltage of 67.275 kV instead. The goal was to come up with an equivalent impedance at the new highside voltage... so that we...

In order to limit the Capacitor Outrush current for two 14.4 MVAR and one 18 MVAR 36 kV Capacitor Banks, it was determined that an 800 uH reactor will be required--for a General Purpose Breaker. What would be the corresponding reactor size when using a Definite Purpose Breaker instead?