SPD Requirement on ac-side of grid-tied PV system

[hungryeng]

I am working with a 2800KWAc PV system and have been looking into whether SPDs are required on the AC Combiner.
Here is the whole system: 14 Inverters of 200KW, combined into 2 AC Combiners (7 per combiner). Those two inverters are connected to a XFMR tied to the utility.

Do I NEED to have a Surge Protection Device on the ACPs and why? In what case don't I need it? For clarity, the inverters are equiped with both DC and AC SPDs.

Thanks in advance

 

[jaggedben]

If you are asking about code requirements it's not required.

Systems this size are not my thing but I think the decision would involve a risk assessment and consideration of whether the inverter manufacturer's SPDs are enough. That is, it might depend more on the site (e.g. how frequent is nearby lightning) than on any info you've given us.

 

[hungryeng]

Thank you, I take it that 242.14(C) does not apply as it is not a separately derived system.

 

[ATSman]

Thank you, I take it that 242.14(C) does not apply as it is not a separately derived system.

Aside from what the NEC requirements are and based on our experience in The Real World, we recommend installing as many SPDs that the budget can afford. The ones supplied my the manufacturers are minimal at best. We ran into a weird incident 11 yrs ago at a major TELCO central office here on the west coast that almost took out the whole facility. The utility equipment was the source of the failure. See attached field report that was condensed from the original.