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  1. wowski

    Transmission Line negative sequence impedance

    We have twin EHV transmission lines approx 80km in length which are closely in parallel for their entire lengths, and are not transposed. Using Transmission Line Impedance calculators with the physical phase positions indicates that the negative and positive sequence impedances are not equal and...
  2. wowski

    Rounding REAL numbers

    I can’t find an Fortran function that rounds a real number to a given decimal place (such as ROUND(x,y) in VB). The only way I’ve found of doing it which works but is ugly is, for the case of wanting to round to the third decimal: dummyVar = 123.456789 dummyVar = TRUNC(dummyVar * 1000.0) /...
  3. wowski

    converting a .lib to .obj files

    Is there any way to split a .lib file back into the .obj files used to construct it? It would be very useful if anyone knows of a way to do this.
  4. wowski

    HVDC model - CDCAB1

    The psse manual is only an excerpt from the model description. I am looking for a more full description of states and how to perform certain tests on the model.Eg. cable faults etc.
  5. wowski

    HVDC model - CDCAB1

    I am trying to track down the description of a HVDC PSSE model, known as CDCAB1. Unfortunately the psse manual is a bit lacking in the description. Does anybody know where I may be able to obtain this information from- it must be out there somewhere. Thanks
  6. wowski

    Transformer differential protection

    From experience with the KBCH it is not always obvious the vector corrections needed for different transformer windings. I am not familiar with the Siemens relay range, but I know with the KBCH you can read the actual differential values the relay is seeing while on load. If this is possible...
  7. wowski

    Shipping of oil filled equipment

    We are looking at having a 50tonne reactor moved, and one of the big issues is the weight of the device. It would be a lot less expensive to ship the device with the tank empty of the insulating oil. What are the problems which could be encountered if this was done. The reactor oil needs...
  8. wowski

    Cable termination earthing

    I have been asked to looked at the termination requirements for two new 12MVA 33/11kV transformers. The specific question I have is to do with the earthing of the lead on the single core cables at the termination points. Is it better to only earth one end to prevent any circulating currents in...
  9. wowski

    armonic vs trnasient analysis

    The inrush current when energising a transformer has a large 2nd harmonic component, which is transient. i.e. if trying to analyse with a FFT the period in which oscillations occur needs to be sampled at a frequency of at least twice the highest required harmonic. The FFT on this data would...
  10. wowski

    Load growth analysis

    Thanks for the reply, we do have all the HV feeder load data available for the past 10 years, I was just wondering what other data I should collect which should be of use in correlating the MD's to other effects (like weather). Your suggestion of light levels and rain may prove useful. Are there...
  11. wowski

    Load growth analysis

    I am trying to study trends in load growth for our region over the past 10 years or so, to be able to predict future load growth. In forming a model, what data would be useful. i.e. I know there is a relationship between maximum demand and temperature, but what about other environmental effects...
  12. wowski

    Change line colour with simple script

    I'm new to script programming in AutoCAD, the application I'm trying to write is to use EXCEL to automatically change the colour of lines in an existing AutoCAD drawings. I can write the Excel VB code fine, I just need to know if there is a simple way to change the colour of a line if you know...
  13. wowski

    Excel File Size & Memory Limitations? How best to proceed?

    I have experienced the same sort of problem when developing an Excel spreadsheet with a userform with a lot of input boxes. I tried unloading add-ins and all sorts but nothing seemed to work. Curiously I found that once I seemed to reach the memory limit, if I closed down excel, then loaded the...
  14. wowski

    HV cable pressure testing

    In my previous post I did not mean to suggest that DC was more destructive than AC( although electricpete did make some interesting points on that subject) just that DC had a higher insulation breakdown voltage than AC. Maybe my reply could have been better phrased. As for the statement that a...
  15. wowski

    power factor

    Theoretically your KWH shouldn't change. The power factor is a measure of the ratio between real (kW) and reactive(kVAr). You can improve the power factor by increasing your kW load and keeping the kVAr component the same, or by reducing the kVAr and keeping the kW the same (as you say you will...
  16. wowski

    50 HZ Magnetic field reduction

    In our experience when dealing with power cables the only effective way to shield sensitive equipment from power cables is to increase the distance between them. Cable shields/ armours shield against electric fields but not magnetic.
  17. wowski

    Eddy Currents in Gland Plates

    This is a problem which we have found in the past, especially with large services. There have been a couple of ways around it. (i) as stated before use non-ferrous gland plates , i.e. aluminium or brass, but you will also have to be careful with your choice of gland materials. Aluminium is known...
  18. wowski

    Checking if a Query already exists in Access

    I am having a bit of a problem with VB in Access, I can not find any methods to say whether a particular query already exits. There used to be an IfExists method which does not seem to be supported. Does anyone know how I could achieve this?
  19. wowski

    Service Problem

    The cause may be internal or external, if your neighbours are having the same problem then there may be a neutral problem, or overloading of the supply cable/overhead line. If it is only you that is effected (you say that it only happens in part of the house so this would seem likely) then check...
  20. wowski

    how to desing a 16QAM using MATLAB SIMULING

    Please could you clarify a 16QAM as I am not familiar with the acronym.

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