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  1. ElectricRob

    Fuse and Feeder Settings

    A few of our blown fuses didn't have an apparent cause (and no corresponding faults past feeder breakers), but several were due to L-G secondary faults within the substation (arrester failure, voltage regulator failure, snake, squirrel, etc.). In some cases the first fuse would blow and then...
  2. ElectricRob

    Fuse and Feeder Settings

    I've always tried to set feeder overcurrent settings based on the rating of the conductor rather than the feeder load current (but I've never had a substation that only has one feeder). If there are normally open ties, you want to be able to pick up load from additional feeders if necessary...
  3. ElectricRob

    Power Line walk down before energization

    I used to inspect distribution lines before signing off on RUS Form 990's and found countless poles that weren't guyed properly. Linemen seem to think nothing of eliminating anchors or shortening guy leads for their own convenience.
  4. ElectricRob

    Paralleling Substation Transformers

    Replying to Palletjack, Splitting the bus and installing a tie breaker is probably the best option, but that adds to the cost of the project. In 25 years, I've never submitted a budget that didn't get cut (nor have I ever seen a CFO take the blame for the resulting equipment failures).
  5. ElectricRob

    Ampacities for Aluminum Overhead Electrical Conductors

    A previous utility that I worked for built several 115 kV lines using 959 ACSS-TW. These were all either radial lines to distribution substations or were normally-open loops. Prior to switching over to the ACSS-TW, we used 795 ACSR as our standard transmission conductor but determined that the...
  6. ElectricRob

    Open Wye Primary / Open Delta Seconday Banking Connection

    If the meter was replaced, and the old meter was electromechanical, it's possible that the old meter was registering slow and the new meter is just correct. I'd be interested in the knowing their typical consumption before and after the installation. Before my utility switched to solid state...
  7. ElectricRob

    What equipment and elements would you need to tap a 69 kV line?

    Minimum would be a three-way switch on a pole, if you are willing to accept that a fault on the tap will be cleared by the main line's protective device(s). You also have to be willing to accept that the line will be radial from there to the substation. If budget allows, I like RRaghunath's...
  8. ElectricRob

    Substations - Rock vs. Grass

    What's interesting to me is that all of the substation ground grid calculations that I've seen assume there is about 6 inches of gravel in the substation (3 inches of crusher run/fines, then 3 inches of larger gravel). In reality, its rare to find a substation with anywhere near that much...
  9. ElectricRob

    25 MVA transformer protection

    I hang out in the NESC world, so there may be other considerations if the NEC applies to your application, but... It sounds like the only thing connected to the 13.8 kV side of the transformer will be the fuel cell system. In the event of a fault between the transformer and the 13.8 kV...
  10. ElectricRob

    Estimating transformer in rush.

    Potential inrush problems aren't just limited to tripping feeder breakers. You should also take a look at the source impedance and estimate the likely voltage dip that will result from the inrush current. Several months ago, we connected a new industrial customer to a 69 kV radial transmission...

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