Surge Protection For Solar Panels

[Peter Topp]

When I first installed my first solar panels I saw that I needed Type 2 surge arrestors for lightning protection.

My series pv array would have to be less than 145vdc open circuit for the inverters I was using.

I started looking and asking for dc surge arrestors. I did find them but they were very expensive compared to the ac ones.

I did a little more investigation and this is what I conlude from my research.

 

You can use a standard type 2 surge arrestor that you would use in your home  DB board 230vac and it will be good to protect dc even at a higher value  typicaly up to about 300vdc.

This is because ac is measured in rms value and is .707 of the peak value which makes the dc value higher.

The surge arrestor protection component is a metal oxided varistor.

Type 2 surge arrestors can be used for ac or dc.

I had some 230vac surge arrestors spare and used them in my installation.

 

 Later I decided to change my inverters to grid tie.

When I changed my inverters I had to change my pv array to have more panels in series.

The inverters would allow 580vdc open circuit. My pv array would be 450vdc open circuit max. but I wanted  the protection to be higher for me to add more pv panels later.

The surge arrestors I had  would no longer be suitable for the installation.

I started my search again for suitable surge arrestors. 

Larger value surge arrestors were expensive but I did find one place that was very reasonable.

I evaluated the costs and this is what I came up with. The drawing is below.

You can use your standard 230vac surge arrestors in series and for a sigle series pv array you would need 3 surge arrestors to protect a pv array up to about 600vdc.

I hope this will help anyone looking for suitable surge arrestors for protection.

Simple any easy to install.

 

 

 

[___]

1 hour ago, Peter Topp said:

The surge arrestor protection component is a metal oxided varistor.

That's one kind. There's also the kind that uses a spark-over gap, sometimes filled with an ionizing gas.

When it comes to lightning strikes, a MOV is probably not going to do much. The MOV also destroys itself when it does it's work. In other applications it is sometimes paired with a fuse, so that the fuse blows when the MOV is pushed into conduction (ie breaks down), but not in this application :-)

The good news, as you indicated, is that the MOV works for AC and DC, and is cheap enough.

[Peter Topp]

I had a lightning strike just after I installed my first pv panels and inverters.

I lost my electric fence, some security cameras, pvr, intercom, gate motor control and  tv.

I did not want to check my inverters as I was convinced they had been damaged.

To my supprise the pv panels and inverters were just fine when I checked so I guess the MOV's do help.

I know nothing helps for a direct strike.

Spark - over gap devices last longer where the effects on an MOV is cumulative thus having a shorter lifetime.

 

 

[SilverNodashi]

I prefer using Type I + II (Type 1 + 2) surge arrestors. They are far more expensive than the normal Type 2 surge arrestors, but I would rather be safe than sorry.