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  1. Blackberry77

    Zig Zag Transformer Sizing

    Hi, I'd like a sanity check on my calculations for a zig zag transformer. I followed IEEE Std C62.92.4 System Voltage - 44 kV Using 100 MVA base Base Ohms = (44000)^2/100000000 = 19.36 Ohms Base Amps = 100000000/(44000)*(1.732) = 1313 Amps Three Phase Fault Duty = 6.4 kA Three Phase Fault MVA...
  2. Blackberry77

    44 kV Transformer Expulsion and Current Limiting Fuses

    Hi, I have a project requiring a 44 kV transformer rated at 250 kV BIL primary. The vendor is stating that expulsion and current limiting fuses cannot be supplied at 250 kV BIL. Do I forego these components in the transformer or have them supplied with a 200 kV BIL rating? Thanks in advance.
  3. Blackberry77

    AmpCalc Cable Libraries

    Just getting into using AmpCalc and trying to model cables that are not within the default libraries provided with the program. How do you all go about inputting your own cable library typically? The manufacturer data sheets does not have half the data that is required in the program. Does...
  4. Blackberry77

    7 MVA, 600 V Motor Loads

    We have a Client that is requesting a 7 MVA motor upgrade at their facility by adding a 44kV-600V power transformer and some switchgear. Now, this as a requirement requires switchgear with ~7000 A requirement at 600 V. This would not be an easily obtained item. Would our best bet to split the...
  5. Blackberry77

    Running CAT5e in Conduit with AC/DC Control Cables

    I always though running CAT5 cables in conduits with AC/DC control cables (120 VAC, 125 VDC) was a no go. However, I am now being told that running armored CAT5 could be acceptable as the conduit is just a sleeve then. We are in Canada, can anyone comment here? Thanks
  6. Blackberry77

    OPGW

    Hi, If I have an overhead line with OPGW at the top and have it down pole grounded every number of poles are surge arresters required on the line?
  7. Blackberry77

    Wind Farm Grounding

    Hi, I am doing a grounding study for a wind farm. The turbine areas have high resistivity layers (granite) and it is hard to obtain low step and touch potentials and GPR. The system is as follows: YY autotransformer with a buried delta several mile long overhead collector line of ACSR with 5...
  8. Blackberry77

    Career Advice

    So I have been working as a field engineer for the past four years. I have the opportunity now to complete my P. Eng and have been toying with the idea of leaving the company or switching to another department. I have been offered a job in another department as a construction project coordinator...
  9. Blackberry77

    Starpoint of current transformers

    I am having a problem understanding the reason for the starpoint connected in a certain way. For example, I know by convention that in differential protection, the starpoint of both CT's covering the zone of protection is always pointed towards the protected object. Why is this the case, is it...

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