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  1. MatthewDB

    Drone does not take down two planes in midair collision.

    Those arguing against it being an "engineering failure" may not be aware that we already have a system in place that would prevent these crashes - Terrain and Collision Avoidance System - TCAS. It is already in all transport aircraft. The collision part uses GPS broadcasts associated with the...
  2. MatthewDB

    Union Pacific rail yard in North Platte - Tesla Fire

    I want anyone thinking that the Tesla could have possibly shocked the fireman to draw the complete circuit for me. I fail to see it as being conceivable. "A path to ground" only makes sense if the source is a ground bonded system. Note that many EE's don't like the term "ground" as it results...
  3. MatthewDB

    MV Switch vs Breaker for Unit Substations

    I'll start with I'm glad to see people recognizing the specific danger found in the MV to LV transformer secondary prior to the downstream LV breaker. The high transformation ratio found at this location, especially at higher MV voltages means that clearing time on a secondary fault is measured...
  4. MatthewDB

    Step-Up Transformers fed from Autotransforer

    I did exactly as you propose years ago. We used a standard commercial variac (Variable auto-transformer) with a motor operator and a transformer. We had a custom transformer built that had many voltage taps available so we could just use one transformer and get all of the desired voltage...
  5. MatthewDB

    Why are Power Grids so Large?

    At a supercritical steam plant, they are. (Coal or combined cycle gas turbine's steam bottoming cycle.) Nuclear power plants run sub-critical at much lower pressure. BWRs run around 1000-1100 PSI and PWRs run 900-1000PSI. The steam dump pressure drop is far lower and hence less erosive than...
  6. MatthewDB

    Why are Power Grids so Large?

    The reason nuclear plants are run all out is economical, not technical. The issue is that fuel purchase and disposal costs amount to less than 10% of the total annual expense. Once construction and decommissioning is added in, the variable cost of producing power drops to ~5-7% of the total...
  7. MatthewDB

    Boeing 737 Max8 Aircraft Crashes and Investigations [Part 3]

    The A320 didn't kill anybody? Air France Flight 296 The stunt with passengers onboard killed 3. Another poster mentioned AF447. That was a A330 not A320 but it was a over-complex automation caused crash. What about Indonesia AirAsia Flight 8501? Very similar to AF447. Pilots can fly...
  8. MatthewDB

    Confessions

    My first boss after University was previously a startup engineer for Bechtel. He shared the story where they had a breaker and a half substation for the power plant, so the generator had two breakers connecting to the grid. During warmup, they would open a disconnect and cycle the breaker to...
  9. MatthewDB

    Water cooled reactors and chokes

    Tamura makes water cooled chokes. The parts I'm familiar with are made by their Japanese division, but they're a worldwide corporation.
  10. MatthewDB

    Confessions

    I got a part made in inches when I designed it in mm. Got a part that was 25.4 times bigger than expected. Fortunately they were tiny parts so the duplicates weren't too ridiculous to deal with.
  11. MatthewDB

    Who blocks zone 2 / zone 3 reclosing?

    SCADA is very old. Systems were in place by the 1920's. They were based around automated telephone equipment. Rotary phone selectors were used to select a specific channel, which could be either a reading or a control. For a meter reading, a voltage, current, PF, etc. would be converted into...
  12. MatthewDB

    Allowable number of startups for a 132KV transformer

    Whenever I hear about using a delta-wye generator step up transformer in reverse to feed plant service, I think of the Detroit Dam Powerhouse fire that occured in 2007. Detroit Dam Powerhouse is a 100MW plant in Oregon, USA, owned and operated by the US Army Corps of Engineers. The plant has...
  13. MatthewDB

    Miami Pedestrian Bridge, Part VIII

    One option would be to make the two halves equal in weight. Make the short span really thick to act as a counterweight to the other half.
  14. MatthewDB

    Converting MV generators from solid ground to LRG

    I honestly don't know if they used a kirk key interlock or used procedural checklists before opening the cabinet. I was a 2nd tier subcontractor so I wasn't familiar with any of the operating procedures. Making it a kirk key with the generator breaker inter-locked would be a really good...
  15. MatthewDB

    Cross Compound Generators' - Why is only one grounded?

    If the generators are wound with a different pole pitch*, you do not want to 4 wire parallel them. Different pole pitches result in different harmonic spectra of line-neutral voltage distortion. This will cause a circulating harmonic current if the generators are paralleled including the...
  16. MatthewDB

    Converting MV generators from solid ground to LRG

    I have been in several large hydropower stations where they used a single grounding resistor per machine group. (A group of several main generators, a station service generator and a step up transformer all on one bus, repeated several times.) All of them were USACE so I suspect this is a...
  17. MatthewDB

    Converting MV generators from solid ground to LRG

    The zig-zag transformer acts as a grounding transformer. It gives you another neutral independent of the generators. Another common option is to use a wye-delta transformer. With wye-delta, the resistor can be either from the transformer wye to earth or the wye is solidly grounded and the...
  18. MatthewDB

    Transformer Strange Inrush Current

    When the residual flux is high, it can help you or hurt you depending on where you energize the line. I wouldn't expect de-magnetized to be always better, I would just expect it to be more consistent.
  19. MatthewDB

    The google expert

    You're right! I need to not dwell on any of it, because it will come around again. I'm a driven person so patience is hard but this is certainly one of those cases. Something I've caught onto over the years is figuring out what kind of student / engineer a co-worker is with regards to the...
  20. MatthewDB

    The google expert

    There is a presumption in your post, that I'm not ready to share everything backing up my work. That's not the case. I keep everything on a shared folder that anyone in the division is free to review. I make it know how it is organized. During a meeting I'm totally fine with pulling it up...

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