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  • Users: Dobber1978
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  1. Dobber1978

    Remote Ground - Ground Fault Currents - Affects on wildlife

    Does anyone know of any papers/articles that discuss remote ground grids / ground fault current and their affect on wildlife? Does anyone have experience with this? Currently working on a substations design where the sub is basically on bedrock with high impedance to earth and can't achieve...
  2. Dobber1978

    Transformer Tap Changer Location - Primary or Secondary

    Just looking for some information on why tap changers would be spec'd on the primary or secondary of the transformer. Scenario - 44kV/13.8kV - delta/wye - 15/20MVA - online tap changers Primary side taps - This is the less expensive option - This is the more common option Secondary side taps...
  3. Dobber1978

    Cable Tracers for Steel and Aluminum Armored Teck

    Has anyone used equipment that has reliably traced steel and aluminum armored Teck power cables? Having issues on site when trying to trace a cable from the panel board out to the end load. Ideally would like to be able to do this live so we don't have to wait for down day to trace them out...
  4. Dobber1978

    Efficiency of Power Factor Correction Capacitors

    I have gotten involved in an energy study and the question about adding power factor correction to try and reduce line current came up. The client's design criteria currently states 0.9PF and we are looking at increasing this to 0.93PF. As this is a energy study the question of how efficient...
  5. Dobber1978

    Horsepower Calculation

    Can someone confirm if this works to calculate horsepower for a motor? I had some metering data provided on a 700hp motor. One of the measurements was kW and I was wondering if I can take this divide by 0.746 to get horsepower. This would basically give the "electrical horsepower" then if I...
  6. Dobber1978

    Pavement inside substation

    Has anyone seen a substation paved? I can only recall ever seeing them with crushed gravel. Looking at 230kv to 13.8kv or 13.8kv down to 600V. Thanks,
  7. Dobber1978

    Grounding Question

    On site we have construction going on and a question was posed to me today and would like other peoples options on it. They are going to be digging around the existing 4/0 bare copper ground cable that runs around the main building and I was asked if there is a fault to ground if there any...
  8. Dobber1978

    Blasting

    I have been asked to do a comparison on different blasting technologies and I have no experience with blasting. The three technologies I have been asked to look at are conventional, Orica's I-kon system, and a PED system(Mine Site Tech). Need to find the pros and cons on each of these systems...
  9. Dobber1978

    OTDR Fiber Optic Test Results

    I have two sets of test results for our single mode fiber optic line, one done at 1310nm and one at 1550nm, I was under the impression that I should get a little higher losses at 1550nm but this was incorrect as the OTDR was showing much higher losses at 1310nm, Can anyone explain? Thanks Jeff
  10. Dobber1978

    VFD vs Soft Start vs Fluid Coupler

    Trying to put together a list of pros and cons for each of the mentioned. We would need 2 drives each one running a 500HP mine dewatering pump, one motor would be on all time and the other would be to pick up the slack, we would like to keep both the same to reduce spare parts so the option of...
  11. Dobber1978

    4th Harmonic Created by Transformer

    We have had an issue on site where there was a intermittent 4th harmonic, today we finally managed to recreate the problem by energizing a large transformer. Could anyone explain why / how this transformer is creating these?? I was always under the impressions that harmonics were usually...
  12. Dobber1978

    Non Standard Inverter Design

    I have an idea, just want someone to tell me why it's a bad idea. I am thinking about an inverter design that does not use solid state but using a DC motor turning a AC generator. Need more out you increase the current to DC motor to increase the torque to increase the output power. The two...
  13. Dobber1978

    Bare Copper Through Concrete

    Does anyone has information on running bare copper cable through concrete? This came up in a job I am working on and my worries are that either the cable or concrete will corode creating a weak point in my ground system or concrete pad, Thanks dob
  14. Dobber1978

    Speaker Resistance

    Got into an argument the other night about speaker resistance and what it really means. I was fighting that this was an impedance that takes into account both the resistance and inductive properties of the speaker, basically the Z at a certian frequency. The other guy was saying this was a...
  15. Dobber1978

    Power System Website Request

    Does anybody know of a good webiste for power systems? I am a recent grad of electrical engineering and am trying to find a website that shows some pratical applications of power system analysis, calculations and theory. Thanks Dobber
  16. Dobber1978

    Ontario Electrical Safety Code - Transformer Spacing

    Is there anyone that can direct me to a section in the OEC that states how far apart transformers have to be installed. Right now I am tring to place two transformers outside a building, both are 13.8/600V, 1500KVA, liquid filled. I think I have all spacing requirements for the building...
  17. Dobber1978

    FR3, Envirotemp Transformer Dielectric Fluid

    I am trying to find someone with a little experience in using this fluid. Cold start up requirements, -20C and colder Environmental requirements in Canada, Good stuff about it, Bad stuff about it, and anything else helpful to myself. Thanks
  18. Dobber1978

    Step and Touch Potentials

    All, I am trying to do some step and touch potential calculations following the methods outlined in IEEE std 80, 2000. The values I am getting are not very reasonable, I think the main problem I am having is calculating my maximum grid current, and right now I am using the available fault...

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