Array Touch Voltage - Corrosion

[Matt_M]

After our recent NICEIC inspection, we were advised to earth ALL arrays by the inspector.

This is apparently common practice in other countries due to the chance of capacative coupling causing an AC voltage to occur on the panel array.

Due to the various safety features used in inverters, we were a little sceptical about this, however, upon testing, our rig did indeed have a substantial AC touch voltage.

The inverters we were using are Soladin 600's, and we recorded a voltage of 20v AC on the array frame.

This could cause corrosion in the long term, and to prevent this we are going to be earthing all installs from now on.

I would be most interested to hear if other people are seeing the same traits. Give it a go and measure your next install.

Thanks,

Matt

 

[Markc]

Was this an Approved NICEIC inspection or a MCS NICEIC inspection?

 

[Matt_M]

MCS NICEIC inspection

 

[Markc]

After our recent NICEIC inspection, we were advised to earth ALL arrays by the inspector.

This is apparently common practice in other countries due to the chance of capacative coupling causing an AC voltage to occur on the panel array.

Due to the various safety features used in inverters, we were a little sceptical about this, however, upon testing, our rig did indeed have a substantial AC touch voltage.

The inverters we were using are Soladin 600's, and we recorded a voltage of 20v AC on the array frame.

This could cause corrosion in the long term, and to prevent this we are going to be earthing all installs from now on.

I would be most interested to hear if other people are seeing the same traits. Give it a go and measure your next install.

Thanks,

Matt

I must be missing something here so came back a read it again. AC voltage on the panels and array from the inverter? How is this measured and with what instrument? I'm not saying you are wrong I just can't get my head round it. The Saladin has a separating transformer for one. How long have you had this inverter and is it part of the recall units? Did you measure insulation resistance from the panels to a earth terminal of the inverter? If you did what reading did you get there for insulation?

Very strange set of circumstances.

 

[Matt_M]

The insulation resistance was fine (>500).

The voltage was measured using a flying lead connected to an earthing point on a module and tested to the earth bar on the consumer unit.

The Soladin does indeed have a separating transformer, however, it would appear that because it is such a small unit it is not effectively seperating and some AC is "infecting" the DC.

BTW, the manufacturers completely denied this would happen, we tested using a freshly calibrated Fluke 1652

 

[Markc]

The next install I will do exactly that. Very concerning.

 

[Matt_M]

Please do, i would be very interested to hear your findings.

I found it very difficult to comprehend, but it was there.

I will try and find some more info on the matter

 

[Matt_M]

Earthing solar panel frames - Energy Matters - bottom of page

 

[edexlab]

Earthing solar panel frames - Energy Matters - bottom of page

This article is referring to Transformerless Inverters , with these you earth the array anyway (or should do) , the corrosion he must be talking about would be between the copper tube lug and aluminium rails you can avoid this using anti corrosion paste ,or stainless washers between the two disimilar metals.
Also and I'm sure I'm not the only person to think this but in the BRB somewhere it says you should follow manufacturers reccommendations when installing equipment , and in most inverter manuals, it says you should earth array even when there is an isolating transformer.


I've got a pdf called capacitive discharge currents off Sma site which explains the causes and effects it seems to be a problem ,more so with thin film and some other types of module construction , with Tls you can reach upto half the mains voltage, but only a few volts with isolating transformers, worth a read!

 

[PeteC]

There have been some callbacks on faulty Salodin 600's~ I might check it out!

From what I've read, +ve earthing is used to stop corrosion where the array has a good contact to ground ie metal frame stand alone.