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Recent content by jfpe

  1. jfpe

    Why there is a negative current flowing into solar panels

    Is this a new installation? We have seen this on start ups when combiner boxes are connected with reverse polarity. -JFPE
  2. jfpe

    Solar Transformer

    Like Kiribanda said, the LV winding choice depends on the PV system design. See what is required by the inverter manufacturer. With central inverter installations, we see mostly delta LV windings. With string inverter installations, we see mostly grounded wye LV winidngs. If you use a...
  3. jfpe

    Eaton Form 6 Recloser Control

    Eaton support is good, although they are often backlogged. We've seen weird symptoms like this from loose internal connections (buttons, etc.) This is from a Performance Advisory Eaton put out on January 8, 2020. The bug may be relevant depending how old the relay is. Issue Description...
  4. jfpe

    1.25 MW Grid Tied Solar Plant | PV Modules Cleaning

    I would add you are torturing your budget as well. I’ve never heard of daily cleaning for a solar field of that size. In dusty desert or agricultural regions, we may see 2-3 washings per year. For a 1.25MW site, I wouldn’t even expect to see staff on site on a daily basis. Monitoring...
  5. jfpe

    How to design a single phase , 50Hz, 240VAC inverter (grid tied)

    waveboy, What are you planning for a power source feeding your inverter? Where does your isolated 400VDC come from? -JFPE
  6. jfpe

    Low insulation resistance - Utility scale PV plant

    For bad wire management problems on PV sites, I've seen home run wires cut by being dragged over a sharp edge in the racking during install. I've seen where the final torque on the modules and racking is done after the home run wires are in place and the home run wires get crushed. It may not...
  7. jfpe

    Low insulation resistance - Utility scale PV plant

    We see a lot of problems caused by failing module connectors, but only when they are laying on racking or in a puddle. Consider isolating strings within a combiner box and using a Seaward tester. This will give you Insulation resistance of the individual string (along with Voc and Isc). The...
  8. jfpe

    480 V sensing required

    Can you sense on the low side of the transformer and use 480:480 PTs? https://www.galco.com/buy/Instrument-Transformer-Div-of-GE/3VTL460-480-480 -JFPE
  9. jfpe

    Pull out Fuse at VT Drawer in MV SWGR

    Overcurrent protection for the PT secondary? -JFPE
  10. jfpe

    Weird Breaker Tripping

    My initial though was the same as cranky108 - bad latch, but the OP says they replaced the breaker. What are the odds of installing a new breaker with the same failure? -JFPE
  11. jfpe

    Opzv battery leak

    Is your charging voltage correct? Could it be too high? -JFPE
  12. jfpe

    Are electric vehicles really sustainable?

    I also wonder about the environmental impact of battery manufacturing and how recyclable/reusable they are. I worry about all the lithium batteries ending up in the landfill in 10 years. -JFPE
  13. jfpe

    Solar power plant cabling: Allowable Voltage drop from PV string to String Inverter

    I typically see engineers design for about 3% voltage drop on the DC side. Like cuky2000 said modern photovoltaic inverters have a wide input window, so DC voltage drop won't push you outside of the allowable input range. DC voltage drop impacts production, so the designer has to decide if...
  14. jfpe

    NYS PE License without a degree

    bragase, You don't need to call anyone; the categories from NYS are clear. Just write up your experience and submit the application. I've been a PE in New York for just over 10 years. My bachelors degree was in "Science Related to Engineering" from a non-ABET accredited college, so I had to...
  15. jfpe

    protection textbook recommendation

    if you need to test anything, I like Chris Werstiuk's "The Relay Testing Handbook" -JFPE
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