Grounding in two wire utility

[ElieAJ]

I live in a country where the utility sends only 2 wires, a phase and neutral. When installing Photovoltaic systems, we usually have to create our own ground for the electrical system. The G of the inverter is connected to it. This ground also serves as the earthing for the Surge Protection Devices.

A particular installer has connected the metal structure of the PV to the same ground. And a couple of his inverters stopped detecting the grid and required repairing. This happened during a thunderstorm.

Was it a mistake to use the same ground for the PV Structure?
I have watched Mike's video about not grounding PV structures, but in this case, how does one protect from current leakage in the metal structure?


Thank You...

 

[jaggedben]

I don't think it was a mistake by itself. Ground is ground, and it is generally correct for all grounds on a building to be connected to each other. It's possible there was a better route for running one ground wire or the other in a way that wouldn't have encouraged lightning to take the path it did. But it's also possible that nothing besides additional protection (such as surge protectors) could have prevented that damage. Impossible to say without seeing the site.

I've also come to the conclusion that what’s best to avoid electric shock and fires caused by human installed sources of electricity is sometimes the opposite of what’s best to protect that equipment from lightning damage.

BTW I'm not sure if it's the common practice in your country to bond the neutral to ground like it is here in the USA, but here we also create the earth connection at rhe building and bond inverter grounds to it.

 

[ElieAJ]

It's possible there was a better route for running one ground wire or the other in a way that wouldn't have encouraged lightning to take the path it did.

I saw in US codes that when using earthing rods, you put one for the system and one for the equipment then you connect them together. Is it a directive? or just an illustration? Because it would be then interesting if we had a minimum distance between the rods or some rules that add protection to the whole setup.

The neutral that comes from utility is grounded. We don't create the bond between neutral and ground on the site, but I think it happens in the inverter anyway.

I've also come to the conclusion that what’s best to avoid electric shock and fires caused by human installed sources of electricity is sometimes the opposite of what’s best to protect that equipment from lightning damage.

Since the panels are on the roof and not usually accessible, I will replace the grounding of the panels with a warning sign.

It's already Christmas night here, so Merry Christmas to you...

 

[jaggedben]

I saw in US codes that when using earthing rods, you put one for the system and one for the equipment then you connect them together. Is it a directive? or just an illustration? Because it would be then interesting if we had a minimum distance between the rods or some rules that add protection to the whole setup.

Not really, we just ground the system to the existing ground these days. Just like any other circuit. Some older code language made it a lot more confusing than it had to be, and that's been removed from the latest codes.

 

[pv_n00b]

I live in a country where the utility sends only 2 wires, a phase and neutral. When installing Photovoltaic systems, we usually have to create our own ground for the electrical system. The G of the inverter is connected to it. This ground also serves as the earthing for the Surge Protection Devices.

A particular installer has connected the metal structure of the PV to the same ground. And a couple of his inverters stopped detecting the grid and required repairing. This happened during a thunderstorm.

Was it a mistake to use the same ground for the PV Structure?
I have watched Mike's video about not grounding PV structures, but in this case, how does one protect from current leakage in the metal structure?


Thank You...

As with many things "grounding," not enough detail is provided. In this system, you can have system grounding, equipment grounding, and lightning protection. These are all separate issues and need to be discussed as such. You say you don't have system grounding, i.e. you are not bonding the neutral to ground on site. So you have to use inverters that work with an ungrounded AC system. It's not "happening" in the inverter. You either provide system grounding or you don't.
For equipment grounding, it is appropriate to bond the metal structure into the equipment grounding system. This is for equipment protection and safety for people. It is not lightning protection.
For lightning protection, you have to install surge protection on the AC and DC circuits and lightning strike protection for the system.

 

[tortuga]

I live in a country where the utility sends only 2 wires, a phase and neutral. When installing Photovoltaic systems, we usually have to create our own ground for the electrical system. The G of the inverter is connected to it. This ground also serves as the earthing for the Surge Protection Devices.

A particular installer has connected the metal structure of the PV to the same ground. And a couple of his inverters stopped detecting the grid and required repairing. This happened during a thunderstorm.

Was it a mistake to use the same ground for the PV Structure?

ElieAJ your in Lebanon correct? That would be a 230V 50Hz two wire system ?

Do you have online access to the adopted codes there?
If so do you have a link?

Possibly IEC 60364-1?

Do you know what 'Earthing System' is used in your area?

• In North America (Canada/US/Mexico) the feed from the distribution transformer uses a combined neutral and grounding conductor, but within the structure separate neutral and protective earth conductors are used (TN-C-S). The neutral must be connected to earth only on the supply side of the customer's disconnecting switch.
• In France (TT) and Australia (TN-C-S), the customers must provide their own ground connections.

See source:

Earthing system - Wikipedia

en.wikipedia.org

Types of Earthing Systems TN, TT, IT and Earthing Systems – Aktif Elektroteknik

There are distinct types of TN Systems in relation to the arrangement of neutral and protective conductors. They are as follows;

aktif.net

If you can provide that info we can be of better help.