[RE-wrenches] Anti-Islanding Explanantion

[Marv Dargatz]

Wrenches,

I feel compelled to reply here, as I have personally performed all of these tests and listed several dozen inverters over the last 10 years.

The "Utility-Interactive" marking on listed inverters means that they meet all of the Utility Protective Function requirements as outlined in IEEE1547.0, and have been tested in accordance with the procedures detailed in IEEE1547.1.  Most of the functions have a threshold value and a response time associated with them.

The Utility Protective Functions include:

Temperature stability
Abnormal voltage
Abnormal frequency
Synchronization
Interconnection Integrity
DC injection
Unintentional Islanding
Reverse Power
Open Phase
Reconnect after abnormal condition disconnect
Harmonics
Flicker

All of these tests must be performed using equipment that meets certain accuracy requirements, and includes considerations for "manufacturer's stated accuracy" of these functions.

In addition, there are utility related performance criteria in UL1741.  For instance, during abnormal condition tests, the maximum fault current and duration must be quantified and published as a rating.

Just to clarify some of what Peter wrote, the default frequency range is 59.3Hz to 60.5Hz, and the default voltage range is 88% to 110% of nominal.  The voltage must be measured from line to neutral if a neutral is present in the connection (i.e. a Y transformer connection).  In addition, there are outer boundaries that require faster trip times.

Bottom line is, if the inverter has a listing mark on it (UL, CSA, ETL, TUV, etc) and is marked "Utility-Interactive" there should be little or no question as to its' suitability for interconnection.

Hope this helps.


See ya!

Marv
Director of Technology and Support, North America
SolarEdge Technologies, Inc.
Tech Support Mobile:  +530.798.6770
Mobile: +530.392.0356


-----Original Message-----
From: re-wrenches-bounces at lists.re-wrenches.org [mailto:re-wrenches-bounces at lists.re-wrenches.org] On Behalf Of R Ray Walters
Sent: Tuesday, July 19, 2011 10:44 AM
To: RE-wrenches
Subject: Re: [RE-wrenches] Anti-Islanding Explanantion

If you wouldn't mind Peter, I'd like to see this discussion stay on the list.
I'd be interested to learn more about the actual anti-islanding features of inverters.
What you've described seems to just cover the voltage and frequency windows that the inverter will grid tie to.
I was always under the impression (perhaps false) that there were additional software controls to prevent anti-islanding to another inverter.
Bill Brooks seems to know more about UL1741 test procedures.

R. Walters
ray at solarray.com
Solar Engineer




On Jul 19, 2011, at 10:04 AM, Peter Parrish wrote:

> I need to give a group of California educators the simplified
> explanation of inverter anti-islanding. I know the full details are
> quite complicated and have evolved a bit over the past few years, but
> would the following be an acceptable short explanation?
>
> *** Please contact me off-list with comments & edits. Thanks. ***
>
> This is an excerpt from a longer discussion about designing and
> installing grid-tied "Inverter anti-islanding is a requirement of the
> NEC and the Underwriter's Laboratory test procedures. A somewhat
> over-simplified version of "anti-islanding" says that if the grid
> voltage goes out of the range of 216 to 264 Vac or if the grid
> frequency goes out of the range 59.9 to 60.1 Hz, the inverter must
> shut down within one cycle (1/60th of a second). Once in this shutdown
> mode, the grid must come back into compliance (both frequency and
> voltage) for 5 continuous minutes before the inverter may turn on again.
> This is pretty "ho-hum". However, two of our laboratory sessions
> involve building a real, grid-connected PV system. So when our
> students go to turn on their system for the first time, they get to
> experience the "anti-islanding" function first hand."
>
> Peter T. Parrish, Ph.D., President
> California Solar Engineering, Inc.
> 820 Cynthia Ave., Los Angeles, CA 90065 CA Lic. 854779, NABCEP Cert.
> 031806-26 peter.parrish at calsolareng.com Ph 323-258-8883, Mobile
> 323-839-6108, Fax 323-258-8885
>
>
>
>
>
>
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