Surge Protection from lighting strikes

[CBR600]

Hi,

I have been asked by a potential customer about this issue. Is it worth fitting surge protection on a domestic PV system? Apologies if the answer to this is obvious!!

 

[SolarCity]

Unless they're in a pretty high risk area, the answer would be no.

 

[PeteC]

I too have this question and have been trawling through the regs:

BS 7671:2008 makes reference to "if required" but not how to determine

BS EN 62446:2009 (in force 01.07.2010) does not give installation guidance only recording of overvoltage protection in the document handover wiring diagrams.

IEC 62548 Ed1 (draft for consultation) gives the following standards:
5.3.3.2.1
Overvoltage protection with surge arresters should be provided when the PV power system meets any of the following criteria:
a) supply of critical loads (eg telecom.repeater stations)
b) the PV array has a rated capacity greater than 500W
c) the PV array is protected by a lightning protection system
62548 are the PV installation to grid harmonizing standards that are still being reviewed by the IEC TC82 committee, and will eventually supersede/extend our 712~ countries are still battling over it's inclusions.

The company I work for are installing a 18KWp system using 2 Fronius IG plus 120 inverters.
Their design spec. is minimal to say the least, and I've been dumped with commissioning it!
Fronius say there is no need to protect their inverters with surge protection but what of the array, when there is an LPS system bonded to the framework, and the DC cables are have no grounded shield or containment conduit? The LPS must be a low risk system as I can see no air rods and there are higher building surrounding the site~ but it is a medical center which has high EMI protection in the regs.
I would have thought it a wise choice to protect the modules anyway.

I'm going to contact the LPS contractors myself on Monday (Thunderbolt, London)

Any advice gratefully received.

 

[TedM]

MCS standards require that you comply with the PV Installation Guide - http://www.electriciansforums.net/photovoltaic-solar-panels-green-energy-forum/23511-pv-guide.html

This says -

2.2.4.1 Lightning Protection Systems

Where there is a perceived increase in risk of direct strike as a consequence
of the installation of the PV system, specialists in lightning protection
should be consulted with a view to installing a separate lightning
protection system in accordance with BS 6651.

Note: It is generally accepted that the installation of a typical roof-mounted
PV system presents a very small increased risk of a direct lightning strike.
However, this may not necessarily be the case where the PV system
is particularly large, where the PV system is installed on the top of a tall
building, where the PV system becomes the tallest structure in the vicinity,
or where the PV system is installed in an open area such as a field.

If the building or dwelling is fitted with a lightning protection system
(LPS), a lightning protection installer should be consulted as to whether, in
this particular case, the array frame should be connected to the LPS, and
what size conductor should be used.

Note: In some cases it may be possible to forgo bonding to the LPS if the array
frame is sufficiently far away from it. A system for determining whether
it is necessary can be found in BS 6651 – ‘Code of Practice for Protection of
Structures against Lightning’. Alternatively, consult the installers of the LPS.
Where an LPS is fitted, PV system components should be mounted away
from lightning rods and down leads ( see BS 6651). For example, an
inverter should not be mounted on an inside wall that has a down lead
running just the other side of the brickwork on the outside of the building.

and

2.2.4.2 Surge Protection measures

All d.c. cables should be installed to provide as short runs as possible, and
positive and negative cables of the same string or main d.c. supply should
be bundled together, avoiding the creation of loops in the system.

This requirement for short runs and bundling includes any associated
earth/bonding conductors.

Long cables (eg PV main d.c. cables over about 50 m) should be installed
in earthed metal conduit or trunking, or be screened cables such as mineral
insulated or armoured.

Note: These measures will act to both shield the cables from inductive surges and,
by increasing inductance, attenuate surge transmission. Be aware of the need
to allow any water or condensation that may accumulate in the conduit or
trunking to escape through properly designed and installed vents.
Most grid connect inverters have some form of in-built surge suppression,
however discrete devices may also be specified.

Note: To protect the a.c. system, surge suppression devices may be fitted at the
main incoming point of a.c. supply (at the consumer’s cut-out).

To protect the d.c. system, surge suppression devices can be fitted at the
inverter end of the d.c. cabling and at the array.

To protect specific equipment, surge suppression devices may be fitted
as close as is practical to the device.

 

[PeteC]

As per the DTI guidelines bonding to the LPS 2.2.4.1 gives requirements but re SPDs, can be fitted, may be fitted, gives no definative requirement. As with their being no legal requirement to assess a building for an LPS system under building regs/H&S or 7671, I would think that commercial building insurance, would govern taking measures to protect equipment. As in general for LPS, once an assessment has been done, you need to follow the recommendations or be it on your head lies.

I believe consulting the LPS contractor may give me an affirmative route of action.

Plus I'll speak to their MCS assessor, who management try to keep me away from.

Glad I'm making plans to move away from this company. I was bothered the directors may browse this forum, but now I don't give a t*ss! They haven't got a clue.

 

[Igi]

We have a PV site with 40 x 160W BP panels mounted about 4m above ground, at a remote location in Sumatera. There's a grounded 75m high tower about 20m away, the initial assumption was that the PV array would fall within the "cone of protection" of this tower. A recent lightning storm destroyed 4 panels and the Phocos controller. Now we've improved the bonding from the panel supports to the LPS and to the tower. We suspect side flash from palm trees close to the PV array but outside our site perimeter was the culprit, so we've also added 10m high lightning poles between the PV array and the trees. SPDs will also be added.

 

[SibertSolar]

All good info above. Lightning/surge protection is something to be seriously considered and not, as is often the case, looked at in retrospect after the project has been quoted/agreed etc. Often the additional costs can be a bit surprising....

An overview of scenarios and documents relating to the BS 7671 ammendment for the AC side can be found on our website here if that's of any use.

As has been said already, best advice if there is an LPS already fitted is to talk to the LPS design/install guys. In my experience, separation distances are very rarely adhered to (between the LPS and the PV array frame) which invariably means that, in order to protect the inverters, Type1 combined lightning/surge protection will be needed for each inverter input. If the distance between the array and the inverters is long enough then devices are often required at both ends...

 

[bommels]

After considering the
- inverter cost,
- inverter life expectancy (at the time),
- cost of inverter warranty extension, and
- cost of surge protection devices
I decided to have protection on both the AC, and DC side of the system.
It is unclear to me why inverters fall over in the first place, however I reckoned that inverters might not like surges/spikes on the AC in particular.
An inverter is an expensive piece of kit, and the surge protectors could be seen as an additional insurance against a possible early death by attacking the root cause of potential inverter failure - at a lower price than taking out a warranty extension.

The surge protection increased the price of the install by about 2%, as the installer kindly decided not to charge me more than the cost of the devices as he thought it was an interesting exercise

 

[hayden]

Just installed 47kw in italy we use dc overvolt protectors before they get to the inverters as standard - works by grounding above 500v on both + & - side quite pricy thought 125 euros each