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Recent content by redfurry

  1. redfurry

    ETAP Cable Zero Sequence Impedance for L-G faults

    That equation looks correct for a ph-grnd fault. As mentioned by others, Z1, Z2 and Z0 are the sequence impedances for the complete conductor group (i.e. phase conductors and any neutral conductor present). Zn is the impedance of the fault itself (i.e. 0 for a bolted fault). It has nothing to...
  2. redfurry

    Transformer Nameplate Information

    Try a Google Image Search for "Transformer Nameplate". It will bring up dozens of examples of real Nameplates so you can see typical details for yourself.
  3. redfurry

    UW Madison Power Engineering Distance Learning

    Also consider Kansas State University. I took a complete Master's degree through them with a full set of power systems courses. Very happy with the quality. These were live classes.
  4. redfurry

    Modeling a PV inverter for fault contribution into distribution system

    Regarding the maximum fault infeed of 2x FLA. I do not believe there are any standards that address this. IEEE 1547 doesn't mention anything like this because it covers all DG technologies, not just inverters. I have seen the maximum short circuit current listed on different manufacturers...
  5. redfurry

    Modeling a PV inverter for fault contribution into distribution system

    The problem with inverters is that they don't act like a rotational machine. I've also seen numbers of about 1.5 - 2 FLA for maximum fault infeed, but it appears that this is very transitory and only lasts a cycle or so. Like David, I suspect this is due to capacitors in the inverter circuit and...
  6. redfurry

    solar farm

    Solar is pretty safe and quiet. There shouldn't be any problems caused by it due to the solar panels. Yes, solar is much more expensive than most other forms of generation, but with enough government money, it's often worthwhile for a developer. The developer is going to have to consider...
  7. redfurry

    Power Factor Capcitors on Low Voltage Power System

    Others may be able to provide better info, but I suspect that you will have to use a more complicated model. If you are interested in solving a harmonic problem, you will need to know the impedances of the loads at each frequency (may not be constant if you have VFDs). A single lumped load...
  8. redfurry

    Ground fault

    Is the OP talking about a high-impedance fault or a high-impedance grounded system? cuky has defined a high-impedance grounded system. A high-impedance fault is just a fault where the fault impedance (as opposed to the system impedance) is high. For example the equation for a ground fault is...
  9. redfurry

    Zero sequence mutual impedance for underground cables

    Are you sure you mean 'zero sequence mutual impedance'? By definition, sequence impedances do not have mutuals (unless you're talking about ugly cases where there are different impedance paths for different phases). If you are referring to 'phase-ground mutual impedances', then for underground...
  10. redfurry

    Energization of 150 MVA transformer. Inrush current issue

    Just a thought, but have you calculated what the voltage drop will be through the 100 ohm series resistor due to the 150MVA transformer no-load losses. Might be an issue.
  11. redfurry

    Benefit of Customer Load Shift

    Oops. You're right. Guess I should think before I post. I was thinking about the cost of reduced losses. The crudely calculated cost benefit of shifting load should be something like A + B where: A = Reduced generation cost due to reduced need for investment in peaking generation, lower cost...
  12. redfurry

    Benefit of Customer Load Shift

    $685/yr/kw = $0.078 / kwh That's above wholesale price, but less than retail for residential customers. Could be reasonable, depending on who's counting.
  13. redfurry

    Cap Bank - Acoustic noise

    You can have resonance when the ratio of the capacitance of the bank to the system impedance matches the square of a given harmonic see: http://ecmweb.com/powerquality/electric_power_factor_correction_3/ This can happen even when there are no major sources of harmonic load on the system. If...
  14. redfurry

    Network Reduction

    Most power systems analysis books have a section on Y Matrix solution methods which describe 'node elimination'. Try a classic like "Elements of Power System Analysis" by W.D. Stevenson for example.
  15. redfurry

    Network Reduction

    It depends on the type of analysis you are performing. If you are interested in fault analysis, you can do a lot of simplification of a network simply by combining impedances (just using simple series or parallel reduction). If you are interested in power flow then network reduction involves...

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