The fastest growing energy technology in the world is grid-connected solar photovoltaic ( ：Renewables 2005: Global Status Report；, REN21). With an estimated 40 million households worldwide using solar collectors and major growth represented by Japan, Europe and the USA you might be surprised to discover the lack of an accepted uniform safety standard. But that doesn・t mean there aren・t any safety standards, far from it.
In fact, there are too many. For the same reason you can・t plug European electric razors in to USA sockets. They are just different. Each country produces similar products at the same time, and each to their own standards. No less than 19 countries have produced or are working on their own versions of photovoltaic-inverter (PV-Inverter) safety standards.
If that・s not enough to give the IEC a headache, the nature of installation between the EU and the USA are not at all the same. We have multi-contact plugs, and they have AC-disconnects. With the general trend towards the more efficient transformer-less Inverters, there is a real possibility of a dangerous DC fault-current, for example in the case of islanding.
Closing the gap and raising the standard
Leading by example Germany has produced their DIN VDE 0126 standard, of which the most significant part defines the requirements to automatically disconnect from an AC interface; thus isolating the inverter from the mains. Or to put it another way, there is no need for mounting a lockable housing for the AC-disconnect. In fact there is no need for an external AC-disconnect altogether!
But that・s not all for VDE. Anti-Islanding is not just about disconnecting. It・s about knowing when to disconnect, and when not to disconnect. False positives are a direct loss in efficiency. It・s also about disconnecting within an acceptable time frame.
VDE 0126 also defines the need for a residual current monitoring unit (RCMU) for the transformer-less inverter. Sensitive to both AC and DC currents, requirements are defined for single-fault tolerance and preventing DC currents being injection on to the grid.
Global standards can wait; there real need for clearly defined safety standards and Germany has got their first. And Phoenixtec hasn・t wasted any time to produce truly international and VDE approved products.
In isolation, we stand together
Phoenixtec is so confident of their new VDE approved ENS, that they・ve applied it to their entire range of grid PV-Inverters. At the time of writing, so far they are the only PV-Inverter manufacturer to do so!
Application of the ENS26 specification prevents islanding effects by cutting the AC-feed to the public utility. Even better, variations in the grid supply are accommodated by monitoring the frequency and impedance jumps and adapting to drifting values.
But don・t just take my word for it. All Phoenixtec PV-Inverters come equipped with a LCD display and powerful communications interface to continuously monitor internal and grid status. With their EZ Logger you can even keep an eye on your investment from abroad!
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