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thankyou, davidbeach

For a single phase, 285MVA, generator step up transformer (which is part of a 3-phase bank), 23kV - 425kV, how do I calculate the transformer impedance at the minimum and maximum taps? The transformer has an off load tap changer on the high voltage winding.

Thankyou, all, for your input.

Why are generator step up transformers sometimes specified with a high voltage winding rating higher than the nominal system voltage they are connected to? For example, a generator step up transformer connecting to a 400kV system is specified with a high voltage winding rating of 420kV.

Hello rcwilson, Would you tell me the name of the manufacturer of the diesel generators mentioned in your post of 25 Feb 09 22:46? Thanks, bxny

Thanks, rcwilson, for the informative input. Yes I am talking about an ~200MVA gas turbine generator. I am assuming that the high harmonic load is from the variable frequency drive electronics. Is that correct?

Thankyou, all, for your input! I do understand about determining which loads are required for starting up the plant, and going from there. What I am looking for is anyone that is knowledgeable about or has direct experience with these exact circumstances - i.e. static frequency converter (sfc)...

16.5kV is the output of the gas turbine generator. There is a step-up transformer, but it is out of the picture. There is a generator breaker between it and the gas turbine generator. Between the gas turbine generator and the generator circuit breaker are the taps to the static frequency...

My question pertains to a combined cycle power plant, one on one (gas turbine generator, steam turbine generator). The gas turbine generator will have a static frequency converter for starting. The plant will have black start capability, provided by diesel generator. Gas turbine generator output...

The project is located at a government facility overseas, not a US territory and we are not aware of any local code that exists governing such an installation. I am asking if any recommendations exist in some industry standard. I am interested in any engineering/scientific basis for such a...

Actually, that is part of what I am asking. Does some code or standard exist which contains a recommendation for separating duct banks at voltage levels such as these.

Can anyone tell me if there is a 'separation distance' requirement for separating underground ductbanks - for example, one bank with 34.5kV circuits and the other with 13.8kV circuits? How far apart do they have to be (minimum edge to edge dimension)?

To respond to your question, bacon4life, the battery is sized for a 2-hour duty cycle, in an electric generating station. Typically, there will be momentary loads that will energize in the first minute, upon a loss of AC power, and then will 'settle down' after that. As far as your ampacity...

I am sizing the feeder cable for a DC circuit from a 125VDC distribution panel to an inverter. The distribution panel is fed from a 125V battery. The inverter normally draws 5A and during a loss of AC power event, it draws 1200A for the first minute and 1A thereafter, for 2 hours ( the duty...

thanks, again, davidbeach.

Thanks, davidbeach. However, forgive me for being a little dense, but, would you mind expanding on what you mean by 'depends on the connections'? Thanks!

Is there a phase shift through a wye-wye, 500kV-230kV autotransformer with a 'buried' delta tertiary? Or is it a zero phase shift, as is the case with two-winding, wyw-wye transformers? Thanks, in advance, for the help.

We will have a lightning protection system on this roof, as well as the supplemental grounding for the roof mounted HVAC equipment.

My intention here is not to debate whether using a supplemental ground is appropriate. My real interest here is whether a fire hazard would exist. Thanks for all your input. bxny

Sorry. I meant supplemental ground, which is bonded to the building grounding system.