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Recent content by tinfoil

  1. tinfoil

    Clearances to Manhole Access

    You may want to review your locality's Occupational Health and Safety Rules. In my jurisdiction, anyone entering a manhole needs to be wearing a safety harness with a means of hauling/winching them out of the confined space. A Ministry of Labor Inspector would issue a hefty fine (to the...
  2. tinfoil

    3 phase instantaneous power

    I believe that the OP formula works for a delta or three wire system if you assume that all quantities are vectors (i.e. complete with phase angles or expressed in complex notation) One thing that you have to be careful about here is ensuring that you are consistent with the use of RMS or...
  3. tinfoil

    Grounding through a switch

    We would allow grounding through a switch as long as the CLOSED state of that switch is guaranteed in the permit (motor decoupled if motorized, etc), and one can visually confirm continuity from the permitted zone to the actual grounded point(s). For this reason, we would not normally accept a...
  4. tinfoil

    Tamper- and Bypass-proof residential/commercial meters

    I forgot to mention that you can also review your historical billing data to detect instances where a customer diverts legacy power usage. If this year's November bill is much lower than their November bill last year, that raises a flag to check the service out. That will not help if they have...
  5. tinfoil

    Tamper- and Bypass-proof residential/commercial meters

    Our 'Smart Meters' communicate back to the office. They have a 'tamper detect' feature that is pretty good at catching when someone is messing with the meter/socket connection. As others have noted on this thread, that is useless if the bad guys are diverting power around the meter. There are...
  6. tinfoil

    Temporary Transformer + Oil Containment

    OP did not specify locale. All of the answers given were for USA. Setting aside legal/regulatory requirements, your company would still be on the hook for all cleanup and remediation in the event of a spill. The utility next to ours just had a spill, and it cost them about $600k for the...
  7. tinfoil

    Voltage Drop Calculation

    As a Utility guy, I always worry about impacts to other loads. Have you looked at the drop/flicker effects to the rest of the facility? You may have to consider other more sensitive loads on the source side of your transformer. In extreme cases, the Power Utility may specify a maximum flicker...
  8. tinfoil

    345kv vs 500kv

    There's a wealth of transmission unit costs to be found in Link Table 2-1 shows line budget costs per mile for each voltage. 345kV = $1.34M/mile 500kV = $1.92M/mile Tables 3.1, 3.3, 4.4 show similar higher costs for 500kV substations vs. 345kV substations
  9. tinfoil

    Transformer protection fusing

    In general, over-current protection devices (like any fuse) ALWAYS go on the SOURCE side of whatever they are trying to protect. Otherwise, they would not provide any protection!
  10. tinfoil

    metering solutions to avoid being charged / billed while on generator power

    Check with your local utility before you spend any money. There are likely specific rules in place that prevent or facilitate what you want to do.
  11. tinfoil

    Motor Starts per/hour

    Don't forget there's another perspective on frequency of motor starts: voltage sags / flicker on the rest of the system Your facility may have issues with starts occurring too often, if it affects other equipment or even causes nuisance light flickers. Your utility likely has quality standards...
  12. tinfoil

    Soil Resistivity Testing In Winter Season???

    The TESTING can be done. The difficulty is in correlating the <0°C results of frozen soils with the 'warm' results. From what I understand, frozen soil resistivity can vary by a factor of 50 to 100 from 'wet' soil. I am not aware of any industry-accepted way to relate the two.
  13. tinfoil

    Circuit Analysis: Current Angle

    WITHIN the circuit, if you have branches, then the current vectors in each branch can be different. If the circuit is just one 'loop' with everything in series, then, as David points out, with only two connections to each node, the current vectors (magnitude and direction/angle)are the same.
  14. tinfoil

    Is there a standard definition of &quot;minimum available fault current&quot;?

    We spec a minimum xmfr impedance to limit fault currents, and then spec a 'loss equation' to try to minimize operating costs. Seems to work.
  15. tinfoil

    Extra Roll of Cable?

    The main purpose of the 'goof loop' near a splice case is to provide sufficient slack to bring the case down to grade level so that it can be maintained/modified (typically in a van or trailer) rather than while up in the air. Splicing fiber is enough of a PITA without adding "while poised on...
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