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Safe in the sun

Questions have been raised about the safety of solar panels, but schools can take measures to ensure that fire risk is reduced to a minimum

Posted by Dave Higgitt | October 30, 2014 | Security & safety

The uptake of solar PV systems in school and other educational buildings has grown with the encouragement of government incentives that enable owners to benefit from free installation and electricity. However, all new technologies can introduce new risks and recent evidence has provided a further example of the fire risks that can be associated with some rooftop solar PV installations.

The latest incident came with national newspaper reports of a rooftop fire at a primary school in Nottinghamshire that damaged two classrooms. The blaze was reported to be the third such incident involving solar PV panels installed as part of British Gas's Generation Green project, which gives schools free equipment in return for a government green subsidy payment.

Although these incidents are comparatively rare, they are not the first rooftop fires to be linked with solar PV installations in the UK. Elsewhere similar incidents have also been highlighted in the USA, France, Germany and Australia.

At present there is no reason to believe that the fire risks associated with PVs are greater than those associated with any other electrical equipment, but these incidents highlight the importance of ensuring the safety and integrity of all PV installations.

As well as requiring fire and rescue services to formulate appropriate operational guidance for dealing with fires involving PV systems, these incidents also continue to emphasise the need for such systems to be correctly designed, competently installed and regularly tested and maintained. 

PV fundamentals

PV systems are unusual in that the energy source cannot be switched off. If there is daylight falling on a PV panel, it will produce electricity and it is possible for a relatively small array of panels to deliver a lethal shock. Another important point is that PV panels generate DC voltage, which is not always commonly used by electricians in their normal work. In addition‚ because of the current limiting properties of PV cells‚ they may not be capable of producing sufficient fault currents to operate over-current protection devices such as fuses. Once established. a fault may remain undetected, not only posing a hazard for an extended period, but also wasting valuable energy generated by the PV system.

In this way undetected faults may develop into a fire hazard over time. Without fuse protection, elimination of a fire risk can only be achieved by good system design and careful installation alongside appropriate electrical inspection and testing.

In the main, proper electrical commissioning procedures are among the best defences against latent fire or electrocution hazards – although once installed, ongoing and effective electrical testing is also vital. 

Setting the standards for safety

The international standard IEC62446: 2009 ‘Grid-connected PV Systems’ specifies the minimum requirements for PV system documentation‚ commissioning tests and inspections. Compliance means PV system owners should be assured that the installation they are investing in is safe and adheres to an internationally recognised level of expected quality. IEC 62446 does this by setting out the information and documentation that should be provided to the customer following the installation of a solar PV panel system and also the initial (and periodic) electrical inspection and testing required. In short the standard sets out measures to ensure that:

• the PV panels and electrical supply connections have been wired up correctly
• that the electrical insulation is good
• the protective earth connection is as it should be
• there has been no damage to cables during installation.

In the UK the British Microgeneration Certification Scheme (MCS) has adopted the principles of IEC62446 as the basis for its testing and documentation regime. As a result, the fundamentals of the standard are enforced because no feed-in-tariff will be paid unless the installation has been installed by an MCS-accredited installer.

A better understanding and acceptance of the importance of effective installation, commissioning and testing is a fundamental requirement to safeguard the fire safety and integrity of solar PV installations. 

Written by Jim Wallace, Seaward Solar W: www.seawardsolar.com

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