Sol-Ark 12K SPD protection needed?

JackSpeed

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Sep 10, 2021
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Greetings all. New to the forum here and I am installing Sol-Ark 12K's which claim to have integrated "lightning protection" but I'm not sure that I fully trust this due to the fact that it states exceeding 500V PV source may damage the unit. As a second line of insurance I tried to find 500V SPD's but reputable manufacturers like Midnight Solar only have 300V or 600V models. Should I assume the unit is protected from the factory, install 600V Midnight Solar units, or go with the unknown brands of 500V units available? Any suggestions? Thanks in advance
 
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SpongeboB Sinewave

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Lightning/Surge (SPD) protection is intended to protect against arcs from input and output lines (e.g. PV+ PV- AC in, AC out) to chassis ground.

Not a differential overvoltage between those main wires like too high of Voc from the solar or high grid voltage line to neutral or line to line.

They cannot sustain a continuous over-voltage like a high line or high PV voltage over the clamp voltage rating of the MOVs that do the protection.



Products like these are (hopefully) tested with a hipot tester at the factory by applying some maximum voltage between all main I/O lines being tied together and GND (chassis). This tests the insulation inside the unit. The power transistor's thermal interface material to the heat sink is one example of these insulation systems inside.

The SPD devices should turn on at some voltage between the highest voltage seen on those input/output lines and the hipot test voltage.

A 600 V SPD actually turns on somewhere in the 800V to 900V range and the hipot voltage could be around 2000V.

And, lightning only lasts microseconds or milliseconds so the internal MOVs have to clamp that voltage below the hipot test voltage.
 

JackSpeed

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Sep 10, 2021
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Thank you Mopat and SpongeboB for the replies. My panel configuration has a Voc of 410 volts so I am not concerned with that. I do however have the panels on a big metal building on a hill with no trees around so there is potential for lightning. Sol-Ark actually specifies that 550V will damage their units which I am assuming they have tested via meggering but they also claim to have lightning protection built in but after running (2) of their units for a while I am having a hard time trusting their specs or info. Of course as mentioned- time could play a huge role with their ability to withstand any type of surge and lightning is fast.

Midnight Solar has a video where they show a 600V SPD hit with 6500V clamping to right around 600V which would be great if Sol-Ark didn’t specify 550V max. I will check out the Surge Pro’s, they seem to offer a nice range of products.

Have a great day
 

SpongeboB Sinewave

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You will still need to be careful not to over-voltage the Sol-Ark yourself. Having said that, the Sol-Ark most likely just turns OFF when the input voltage rises above 550V DC. The capacitors used may be the actual limiting factor there but the FETs or IGBTs used is more than likely 600V or 650V rated.

Any SPD that uses MOVs for lightning and surges will not protect your PV input voltage from going above 550 or 600 volts. The operation should be the same.

Now you COULD possibly find a HV switch that turns OFF the PV input if it rises about 550V. The best thing is just to design the system so that the PV voltage does not get to 550V at the lower temperature you would expect at your place.

boB
 
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