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

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...

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...

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...

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

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...

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...

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

Overcurrent protection for the PT secondary? -JFPE

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

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

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

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...

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...

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

I'm reviewing the preliminary drawing package for a small (5MW) solar farm. The design engineer has specified low energy analogue (LEA) voltage sensors instead of PTs for the customer owned recloser. Does anyone have concerns or reservations about LEAs? Is the accuracy comparable to PTs...

Are you running oil tests beside DGA? I would trend Water content (D1533) and dielectric breakdown (D877). -JFPE

SparWeb, You're correct, except you mean three strings of cells in series, not in parallel. The bypass diodes allow current to flow when one portion of the module is shaded. FWIW, one of the most common module failures we see is a sorted bypass diode. The module output voltage drops by 1/3...

If the components are from different manufacturers, some inspectors would flag this as a violation of 110.3 (B) "Installation and Use. Listed or labeled equipment shall be installed and used in accordance with any instructions included in the listing or labeling." -JFPE

Whether the grounding bank is technically warranted doesn't matter. If the utility requires it you'll need to install it. Speak to the inverter manufacturer. They should be able to give you grounding transformer design/sizing advice. If the inverter manufacturer can't help you, the Xcel...