Difference between 2P and 3P DC SPDs for PV systems

[nx6]

Hello everyone,
I have a question regarding the difference between 2-pole (2P) and 3-pole (3P) DC surge protective devices (SPDs) used in PV systems.
As I understand it, a 2P SPD protects the positive and negative lines, while a 3P SPD protects the positive, negative, and grounding lines.
My main questions are:

1. Is a 3P SPD simply a superior version of a 2P SPD, offering an additional level of protection? Or are 3P SPDs designed for specific system configurations?
2. In what situations would you choose a 3P SPD over a 2P SPD, and vice versa?
3. Are there any particular advantages or disadvantages to using a 3P SPD in a PV system?​

 

[Daddy Tanuki]

Hello everyone,
I have a question regarding the difference between 2-pole (2P) and 3-pole (3P) DC surge protective devices (SPDs) used in PV systems.
As I understand it, a 2P SPD protects the positive and negative lines, while a 3P SPD protects the positive, negative, and grounding lines.
My main questions are:

1. Is a 3P SPD simply a superior version of a 2P SPD, offering an additional level of protection? Or are 3P SPDs designed for specific system configurations?
2. In what situations would you choose a 3P SPD over a 2P SPD, and vice versa?
3. Are there any particular advantages or disadvantages to using a 3P SPD in a PV system?​

I have to admit i am lost do you have any links to these products? I use midnite solar and they do not even mention what all is involved, only that you put one line on L1 and L2 and one to either ground or neutral (need to look up the books again as I installed mine several years ago and have forgotten exactly how they were wired.

 

[meetyg]

I have to admit i am lost do you have any links to these products? I use midnite solar and they do not even mention what all is involved, only that you put one line on L1 and L2 and one to either ground or neutral (need to look up the books again as I installed mine several years ago and have forgotten exactly how they were wired.

He's talking about DC SPDs, not AC.

@nx6
I too have come around a 3 pole DC SPD in a solar combiner box I have, while two smaller one I have have only 2 pole SPDs.

For example:


The 3 pole ones are actually Negative/Positive module in series with the middle one. I think they do this to increase the voltage rating that these can handle.
I'm not sure why they do this, since the SPD modules themselves come in either 500-600v ratings or 1000v ratings.

Anyways, you want a module that will not exceed the max PV voltage on your inverter (but not less than your PV array, otherwise it will trip easily when under normal conditions).

 

[Daddy Tanuki]

He's talking about DC SPDs, not AC.

@nx6
I too have come around a 3 pole DC SPD in a solar combiner box I have, while two smaller one I have have only 2 pole SPDs.

For example:
View attachment 217126

The 3 pole ones are actually Negative/Positive module in series with the middle one. I think they do this to increase the voltage rating that these can handle.
I'm not sure why they do this, since the SPD modules themselves come in either 500-600v ratings or 1000v ratings.

Anyways, you want a module that will not exceed the max PV voltage on your inverter (but not less than your PV array, otherwise it will trip easily when under normal conditions).

i use the midnight solar SPD for my DC as well, just the DC specific ones. once again nothing mentioned in the literature that I can remember. Not saying anybody is wrong, I am admitting to gaps in my knowledge and now I want to look into it more.