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Posted By Topic: Storage added to existing PV system On Grid

Phazor
Jan 19 2019 11:11

If storage is added to an existing PV system (its been inspected and added to High Risk Database previously)) with outage backup option i.e. islanding suboard supplying essential circuits fed from muti mode inverter does this require another high risk inspection ?
   

pluto
Jan 19 2019 20:16

Yes

It may pay to check that the current grid connect inverter can provide for a battery input and is able to operate in a stndalone mode.

One key point to remember is a grid connect inverter requires a mains supply to be able to operate and to produce an AC output.

No mains supply the grid connect inverter is required to shut down and your expensive battery is of no use at all.
   

Phazor
Jan 20 2019 07:45

Pluto under what category Main parrellel, PV .....
   

AlecK
Jan 20 2019 11:04

Installing a grid-connected inverter comes under "mains parallel".
Installing batteries doesn't, and unless above ELV isn't even PEW at all.
Installing batteries is also not under photovoltaic - which also isn't PEW at all unless above ELV.

But Pluto's right that the anti-islanding requirements for grid-connected inverters mean that adding storage doesn't help.
You need a multi-mode inverter that has a "mains parallel" mode and an off-grid mode. and installing one of those falls under 'mains parallel, as well as having to comply with the contract with the relevant network.

To ensure both safety and compliance would involve changeover switching between these modes that is external to the inverter and set up as for an alternative supply. The internal switching is unlikely to meet the isolation requirements.
   

pluto
Jan 20 2019 12:16

A bit of a "heads up" where the international practices are heading.

In recent weeks the IEC have produced an standard for the requirements for the inverter systems for use with an external energy source. BTW the inverter is known as a "grid connect inverter"; and not as was expected by the AU/NZ joint committee who was using the term "multi-mode" inverters.

Typical sources for this new generation of grid connect inverters being the batteries in electric vehicle batteries, storage batteries (charged by a wind turbine, PV arrays) just to name two typical examples.

Elsewhere the development of mirco-grids is also proceeding as rapidily as possible. This operating mode will require the use of a full current disconnection device between the main switch of the installation and the output of the new generation of grid-connect inverters to allow consumption within an electrical installation with the inverter running in a standalone mode.

The current trends of this new work by the IEC and most other countries in Europe, will meaan that suitable hardware and construction practices will become available in the short term and mean that the current method of using inverters for importing and exporting and the sole use of the AC energy in the electrical installation will change in the near future.

I'm not aware of any inverter hardware available in AS/NZ at the moment and would expect that the new generation of grid connect inverters will need to be software controlled due the wide variation of functions required when the mains supply is available, and is unavailable, or is in an out of voltage and frequency limits conditions.

The current AS/NZS standards will all need major amendments to take in these new developments. I would expect it will be about 2 years before the updated standards will be available.