Thursday, 16 October 2014

Upcoming - IET solar PV code of practice

The Institution of Engineering and Technology (IET) is perhaps most commonly known as the publisher of the Wiring Regulations, BS7671 or as most people know them, The Regs.

The IET Solar PV code of practice (PV-CoP) will be the first PV-specific document that the IET has released and is due to be issued imminently as a draft for public comment.

Guide to the installation of PV Systems - was published in 2002 and its writing was funded by the government (via the then DTI). mostly called the "DTI Guide", was basically a framework for  various PV grant programmes that were running at the time.

Edition 2 of the DTI Guide was released in 06 and was eventually heavily edited and re-issued as the MCS Guide to the installation of PV systems, in 2012. All three publications have always been key documents to UK solar PV installers because, although only installation guides, following them was required in order for most customers to get the feed-in tariff

The IEC, has been working on a PV installation standard. Unfortunately the process requires international consensus.

If you are familiar with our UK PV guides would find much in IEC TS 62548 pretty familiar and all PV installers should be familiar with the content of 7-712. Both documents need updating and 62548 is at present only a technical specification, not a full standard. Although I am heavily involved in the process, I am not sure how these two documents will evolve.

With the MCS guide out of date in a few parts and with the IEC process running slowly, the IET working together with the BRE National Solar Centre decided that the time was right to provide a solar PV code of practice, similar to other code of practices that the IET publish (eg LED lighting or electric vehicle charging). The following is an extract from the scope of the draft PV-CoP:
This Code of Practice sets out the requirements for the design, specification, installation, commissioning, operation and maintenance of grid-connected solar photovoltaic (PV) systems installed in the UK.

The scope of this Code of Practice covers:
o All parts of a grid-connected solar PV system up to, and including, the connection to the AC mains.
o LV and HV connections and components.
o All scales of application, from small domestic systems to large-scale PV farms.
o Building-mounted, building-integrated and ground-mounted systems.
o Grid-connected systems with battery storage.
o Systems with an open circuit DC voltage of greater than 30VDC and less than 1,500VDC.

This covers a lot  more than a simple 4kw domestic install and addresses much larger systems and also HV connections. With this wider scope, it is likely that it will be used as a key document during the design and development of large-scale PV systems here in the UK - an area not really covered by any standards at the moment. It is also fairly likely it will be adopted by MCS to replace the existing PV guide.

there are a few changes proposed, including:
* Array frame earthing - it is proposed that the PV array frame will now need an earth connection in most circumstances
* Earth fault alarm - new requirements for an earth fault alarm
* String fuses - it is proposed that these will only now be required on one of the active conductors
* PV plug & sockets - it is proposed to ban mating of different manufacturer's/models

Many of the proposed changes are anticipating likely requirements that we can see heading our way from IEC, some are lessons learnt and some simply reflect advances in inverters and arrays

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