[ Spotlight: Test equipment ]
manager at Seaward Solar, warns: ‘Due to the current limiting properties of solar PV cells‚ they are incapable of producing sufficient fault currents to operate devices such as fuses.’
Above and beyond Although solar PV installations should be installed and tested in accordance with BS 7671 17th Edition IEE Wiring Regulations, other standards should be taken into account. Incorporated into the MSC is IEC 62446: 2009, which
sets out the information and documentation that should be provided to the customer following the installation of a solar PV system, as well as the initial and periodic electrical inspection and testing required. The standard recognises that only by the provision of adequate documentation at the outset can the long-term performance and safety of the PV system be guaranteed. Seaward Solar’s Jim Wallace explains: ‘The standard
sets out measures to ensure that the solar PV panels and electrical supply connections have been wired up correctly, that the electrical insulation is good, that the protective earth connection is as it should be, and that there has been no damage to cables during installation.’ Also of note is Engineering Recommendation G83/1,
which is the installation commissioning confirmation form for the connection of Small Scale Embedded Generators‚ such as PV arrays‚ of up to 16A per phase with public low voltage distribution networks. Contractors should complete G83/1 with information on various tests‚ system details and a range of supporting information to satisfy the requirements of the distribution network operator.
Kit bag In order to carry out the tests outlined in IEC 62446, a range of instruments are required including an earth continuity and insulation resistance tester‚ a multimeter, a DC clamp meter and an irradiance meter. As Megger’s Simon Woods comments: ‘Many electrical installers will have all the instruments required in their toolbox already, apart from an irradiance meter, but these are now commonly available.’ Dave Sweetman, area sales manager at Di-Log Solar,
states: ‘Selecting a piece of test equipment that suits your needs and budget is vital. However, whatever you choose will need to conform to BS 61010-1 and be CE certified.’ Using such an array of instruments can be cumbersome
and time consuming – considerations that have led to the introduction of a new generation of integrated testers capable of performing all of the tests required. Knowing what tests to carry out and in what order is only
part of the process. The Green Electrician’s Tim Painter, comments: ‘Interpreting test results correctly is a major factor in getting an installation right, as failure to do so can have serious consequences.’
Safety first Despite the guidelines that are currently available, there still appear to be some areas of confusion over the correct test procedure for solar PV panels.
November 2011 ECA Today 47 Standard issue
There is now a new generation of integrated testers capable of performing all of the tests required
IEC 62446: 2009 Grid Connected PV Systems – Minimum Requirements for System Documentation, Commissioning Tests and Inspection not only specifies minimum testing and inspection requirements, but also how the inspection and test results are documented and supplied to the consumer after installation.
In many cases, documentation not only provides
evidence to the consumer that work has been performed correctly, but it also acts as a checklist to an installer and ensures that best practice is followed with the work being undertaken. In the UK, IEC 62446 is incorporated into the Microgeneration Certification Scheme (MCS) and, although the standard is not mandatory, it is effectively enforced because no FIT will be paid to a consumer unless the installation has been installed by an MCS accredited installer.
One area of concern is the testing of protective earthing
and equipotential zones. Jim Wallace of Seaward Solar, comments: ‘There is a requirement to ensure that extraneous metalwork is bonded and the installer is therefore required to perform continuity tests with an ohm meter which complies with the requirements of the 17th Edition IEE Wiring Regulations.’ However, in some situations the solar PV system may
be regarded as being located outside the equipotential bonding zone, and therefore the requirement for continuity testing is not required. Either way, it is prudent to ensure that a continuity meter is available that is capable of carrying out circuit measurements with a current of a lot less than 200 milliamps and an open circuit voltage not exceeding 4V.
Solar power meter
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