2008-01-14
BS 7671:2008 includes a new Section 712 providing additional requirements for safety applicable to solar photovoltaic (PV) power supply systems.
The additional requirements in BS 7671:2008 along with some explanations are discussed in this article. As with any low voltage installation, the general requirements in Parts 1 to 6 of BS 7671:2008 have also to be met which include in Part 5, Section 551, requirements for low voltage generating sets.
Please note that a list of definitions is included at the end of this article.
The risks
The particular risks associated with solar photovoltaic systems are:
PV systems cannot be switched off. Modules produce electricity when exposed to daylight. Hence, unlike most other electrical installation work, the installation of a PV system typically involves working on a live system. Regulation 14 of the Electricity at Work Regulations gives requirements that must be met. Special precautions should be made to ensure live terminals are either not accessible or cannot be readily touched during installation and maintenance. Such terminals will be live at all times during daylight hours. It is important that anyone opening an enclosure is aware of this.
An electrician who has come to work on the electrical installation needs to be aware that there is a second source of energy which will also need to be isolated.
PV modules are current-limiting devices which require a nonstandard approach when designing fault protection systems for the dc side, as fuses are not likely to operate under short-circuit conditions. A different approach to fault protection is often needed, such as sizing the conductors for the maximum fault current that can flow at any given point in the circuit.
PV systems include dc wiring, with which few electrical installers arefamiliar.
PV presents a unique combination of hazards – due to risk of electric shock, falling and simultaneous manual handling difficulties. All of these hazards are encountered as a matter of course on a building site, but rarely all at once. While roofers may be accustomed to minimising risks of falling or injury due to manual handling problems, they may not be used to dealing with the risk of electric shock. Similarly, electricians would be familiar with electric shock hazards but not with handling large objects at heights.
Originally published in Wiring Matters Winter 2007, by John Ware
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Source: IET |
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