my new 3.9kw install

[BruceB]

All SMA inverters have galvanic isolation as far as I am aware.

Jonathan

No, I do not believe so.  The SMA TL series are 'transformerless'.  Galvanic isolation as I understand it means with an isolating transformer.

Regards
Bruce

[Outtasight]

Yep, the TL models are not fully isolated but are considered safe due to other measures.

In order to get away without using a transformer, they use H5 inverter switching topology.  At times in the AC cycle, the AC and DC sides are disconnected by a switch.  During the times in the AC cycle when the two sides are connected, a RCD monitors the AC side for earth leakage current, and if detected, it causes a ground fault signal that disconnects the inverter from the grid and shuts down the system.  They also employ a start-up test of the DC side insulation resistance before connection to further check if there is a ground leak on the DC side.  The disconnect relay is double pole (L and N) and has uses two relays in series so that if one fails to open, there is a backup.

A paper here explains the switching topologies being used in transformerless inverters.

http://www.elkraft.ntnu.no/eno/Papers2008/Schimpf-norpie08.pdf   

[ecotrician]

RCD protection can not be used as primary fault protection, all transformerless inverters need the array frame to be bonded as per DTI guidance note, if TNS or TT then to MET, if TNCS then to earth rod.

SMA guidance in instructions also states this:

Grounding the PV generator
Comply with the local requirements for grounding the modules and the PV generator.
SMA Solar Technology recommends connecting the generator frame and other electricity
conducting surfaces such that there is continuous conduction and to connect them to the
ground in order to reach maximum protection for property and persons.

[firepete]

well mine has not been earthed. should it have been then.

i have had 3 trips on my main circuit board rcd since install. not sure what caused it. but on two ocasions i think i was cleaning the panels outside.

[tange179]

Word of a caution - be careful where you place your earth rod i.e. keep well away from any underground electrical cables as you do not want to be responsible for taking out your street should you be unlucky enough to be hit by lightning 

John

[firepete]

removed rcd protection and now just on a mcb . seems fine

[Alan]

Quote “ Word of a caution - be careful where you place your earth rod i.e. 
keep well away from any underground electrical cables as you do not want to be responsible for taking out your street should you be unlucky enough to be hit by lightning 

John “

Bit OTT

Any house with a T.V. Aerial on the Chimney pot has got more chance of copping one. Thats why lightning protection rods are made with pointed tips to encourage discharge to take place.

If I had a T.V. Aerial on the roof it would be very low on the lists of things to worry about.

Regards

Alan