[RE-wrenches] Inverter 1741 Listing Process
Exeltech
exeltech at yahoo.com
Wed Oct 20 17:01:32 PDT 2010
Matt et. al.,
IEEE 1547, 7.1.1 states "The commissioning test shall be performed to verify that the completed and installed ICS meets the requirements of IEEE Std 1547."
Verification on the grid-tie equipment has been done for you by the NRTL as part of the UL1741 test procedure, which, as Matt pointed out, has IEEE 1547 as a subset.
I refer you back to page iii at the front of IEEE 1547.1, which states: "IEEE Std 1547.1 provides conformance test procedures to establish and verify compliance with the requirements of IEEE Std 1547. When applied, the IEEE 1547.1 test procedures can provide a means for manufacturers, utilities, or independent testing agencies to confirm the suitability of any given interconnection system (ICS) or component intended for the use in the interconnection of DR ("distributed resources") with the EPS ("electric power system"). Such certification can lead to the ready acceptance of confirmed equipment as suitable for use in the intended service by the parties concerned."
[Note: Quoted items in parentheses are mine for clarification purposes.]
Also...
In IEEE 1547.1 Section 6.4, "Documentation" refers to the
documentation we as manufacturers are required to provide with each unit
to the NRTL for audit purposes. The NRTL shows up unannounced, and may
review our test records at any time. The documentation mentioned in
IEEE 1547 is part of our audit trail. "Production test documentation"
is not included with units that leave the factory.
So .. in plain English .. none of the "Commissioning Tests" are required on site of any UL1741-certified inverter. This is not to say an AHJ or utility won't ever ask for them, but if it happened, that would be an AHJ/utility-specific issue.
My $0.02+ from the manufacturer's side of the fence...
Dan
--- On Wed, 10/20/10, Matt Lafferty <gilligan06 at gmail.com> wrote:
From: Matt Lafferty <gilligan06 at gmail.com>
Subject: Re: [RE-wrenches] Inverter 1741 Listing Process
To: "'RE-wrenches'" <re-wrenches at lists.re-wrenches.org>
Date: Wednesday, October 20, 2010, 2:20 PM
Thanks Guys,
Here's an update for anyone who cares.
The specifics I was looking for are included in IEEE
1547.1, which is inherently included in UL 1741. In other words, since 2007, if
you have an inverter listed to UL 1741, it must also meet (by certification) the
requirements of IEEE 1547 and 1547.1. In fact, the sections of UL 1741 that
formerly applied to the Utility Compatibility functions have been removed.
Voido. They are now replaced by IEEE 1547 & IEEE 1547.1.
IEEE 1547.1 is clear and precise about the production test
requirements I was looking for. UL 1741 is weak on the issue. In general,
utility companies rely on IEEE documents and requirements for their guidance. I
see why some of them require field verification of the non-islanding function by
flipping the AC switch off with the inverter running... Well, not exactly.
Technically, the non-islanding function is something else. The
"Cease-to-energize" function is what they are actually verifying in the field.
Here's a short rundown on the issue....
IEEE 1547.1 (Clause 6; Production Tests) requires production
tests for response to abnormal voltage, response to abnormal frequency, and
synchronization. Combined, these would constitute production testing that
confirms the non-islanding functions that are Type tested on a sample unit.
And there's more. This section also requires that the documentation
of these production tests be provided with the equipment.
IEEE 1547.1 (Clause 7; Commissioning) requires some
verification and testing steps. These are allowed to be performed by a qualified
person and the utility may require that they witness the process (at
their option). Inherent to this section is a requirement that
there be a commissioning report generated which contains data related to the
process. "A commissioning test report shall be produced and shall contain
the results of all tests and a listing of the final ICS
settings."
The required steps involved in Commissioning
include: Verification and Inspection, Identifying any required Type and
Production tests that were not performed and performing them in the field;
Unintentional Islanding functionality test; Cease-to-energize functionality
test; Documentation of revised settings.
Understand that all of these steps are REQUIRED AS PART OF THE
COMMISSIONING PROCESS, per IEEE 1547.1.
My focus is primarily on the Commissioning procedure... I'll skip the
inspection and verification steps for this
post.
Note that Clause
7.3 of the Commissioning section requires field performance of any Type or
Production tests that have not been performed. When the manufacturer fails to
include the Documentation of Production Tests with their product, the
commissioning technician has no choice but to do them in the
field.
(NOTE TO INVERTER MFRS: INCLUDE CLEAR DOCUMENTATION OF YOUR
PRODUCTION TESTS WITH EACH INVERTER, PER IEEE 1547.1 Clause 6.4; NOTE TO
INSTALLERS: HAVE THIS DOCUMENTATION HANDY AND LEAVE IT WITH THE
INVERTER.)
Clause 7.4 is the Unintentional Islanding functionality test.
If the unit is connected to the grid via reverse-power
or minimum-power protection equipment (commonly referred to as
non-export or zero-export; relatively rare) instructions are given for testing.
This test is waived if the inverter is certified to Clause 5.7, the
Type test for Unintentional Islanding. (Check) If the unit is not certified to
5.7 and not connected via zero-export protection equipment, this function is to
be tested according to procedures provided by the integrator or the
manufacturer. UL 1741 Listed inverters should be certified to Clause 5.7,
which makes them eligible for the waiver.
Clause 7.5 is the
Cease-to-energize functionality test. This tests that the inverter does not
energize the output (AC) terminals on loss of grid AC. It also checks that the
restart/reconnect time delay (5-minute wait) functions as required. The test is
simple. Run the inverter at any power level and open the ungrounded AC phase
conductors. Verify that the output terminals of the inverter are not energized.
Apply AC power. Verify that the unit waits the required amount of time to
reconnect.
There are two important sentences in this Clause to know
about. The first is that "An ICS that meets the requirement so 5.9
(open-phase type test) and 7.4.1 (zero-export) satisfies the requirements of
this subclause." This means that a UL 1741 Listed inverter interconnected
via zero-export equipment is exempt from this test.
The second sentence to know about is this one: "The
following procedure may be adjusted dependent on an agreement between the area
EPS authority (electric utility) and the system installer." This means
that, every time the utility does not require you to test this function, they
are agreeing to "adjust" this procedure, even if they don't tell you they are.
You are getting a free pass.
Let me repeat that another way... IEEE 1547.1 REQUIRES that
this test be done unless the above-mentioned exemptions are met. As an
installer, you must be prepared for and expect to do this test.
Nowhere in the Commissioning section of IEEE 1547.1 does it
exempt performing the Commissioning steps or producing the Commissioning
test report.
I am of the strong opinion that having the manufacturer's
Production Test Documentation on-hand will go a long way toward gaining
the utility's acceptance of the system without performing
the Cease-to-energize functionality test. I believe that most of our modern
inverters will meet one of the exceptions to the Unintentional Islanding
functionality test. I believe that it is best practice to perform comprehensive
commissioning on all systems, and record the relevant data. I have always found
that doing this and having your documentation together gains respect from AHJs
and utility inspectors. I believe that by doing this, we demonstrate
professionalism and responsibility. Working with utilities in a manner that
demonstrates professional, knowledgeable, and responsible behavior can only
benefit our respective organizations.
Happy commissioning!
Matt
Lafferty
From: re-wrenches-bounces at lists.re-wrenches.org
[mailto:re-wrenches-bounces at lists.re-wrenches.org] On Behalf Of
Exeltech
Sent: Tuesday, October 19, 2010 12:20 PM
To:
RE-wrenches
Subject: Re: [RE-wrenches] Inverter 1741 Listing
Process
boB covered the main points perfectly.
Manufacturers
of UL-certified products are subject to unannounced spot-checks several
times a year by the issuing NTRL to verify the products coming off the
production line are absolutely identical to the products submitted for UL
testing. Any major deviation in the production units from lab-tested
units can result in immediate de-certification and possible recall of any
affected product(s). "Major" in this case could be different
software, mechanical changes, or a substitution of any components that
affect safety or unit operation in any manner with unauthorized components
.. for openers.
By the way .. for anyone who's not met boB in
person .. I had the good fortune to do so at the Midwest Renewable Energy
Fair in Wisconsin this past June. Great
guy.
Dan
--- On Tue, 10/19/10, boB Gudgel
<boB at midnitesolar.com> wrote:
From:
boB Gudgel <boB at midnitesolar.com>
Subject: Re: [RE-wrenches]
Inverter 1741 Listing Process
To: gilligan06 at gmail.com, "RE-wrenches"
<re-wrenches at lists.re-wrenches.org>
Date: Tuesday, October 19,
2010, 12:42 AM
On 10/18/2010 9:53 PM, Matt Lafferty wrote:
Thanks for the info Dan and boB.
What production tests required to maintain listing? Do you
happen to know if there is a different regimen for micro vs string vs
central inverters?
You mean, a
difference between the two when UL, ETL, CSA comes by for their pop
inspection ??
Off hand, I don't see why one inverter would
be given any different kind of attention than the other
type.
The UL/ETL followup inspections are basically to make sure you are
following the proper
manufacturing and testing processes such as,
software version, verification that you are using
UL recognized
sources of parts and materials, hi-potting at the correct voltages,
etc.
They are both grid-tie inverters so the testing
processes are very similar.
I'm sure that Dan will pick up
on anything important that I forgot.
boB
I'm working on developing a detailed commissioning
procedure. Detailed yet generic. There will be at least two versions
for inverters. One for string and one for central. In my book, central
inverters have re-combiners (standalone or integral) and string
inverters don't. I'm trying to understand which functions are tested in the
factory on every unit so I can avoid unnecessary duplication by the
commissioning people.
Thanks in advance for any light you can shed on the
subject!
Matt
Lafferty
From: re-wrenches-bounces at lists.re-wrenches.org
[mailto:re-wrenches-bounces at lists.re-wrenches.org]
On Behalf Of Exeltech
Sent: Monday, October 11, 2010
10:04 AM
To: RE-wrenches
Subject: Re:
[RE-wrenches] Inverter 1741 Listing Process
Matt,
The 5-minute delay is verified in
the group of inverters sent to the test laboratory. Then,
as long as the software and hardware don't change, it's presumed
the delay in all production units meets the value(s) measured in
the tested units.
An alteration in either hardware OR
software can result in a unit being required to completely
re-test (as Bob pointed out). NRTLs get copies of the
source code and can and do periodically compare their copy as
submitted with the original test units to the software being
programmed into the inverters during production to verify it's
the same.
NRTLs conduct unannounced "field audits" by
simply showing up on site and randomly selecting various aspects
of the product for verification -- including the
software.
The overall UL1741 certification process is
extremely complex, very time consuming, and quite
expensive.
Dan
--- On Fri, 10/8/10,
boB Gudgel <boB at midnitesolar.com>
wrote:
From:
boB Gudgel <boB at midnitesolar.com>
Subject:
Re: [RE-wrenches] Inverter 1741 Listing Process
To: gilligan06 at gmail.com,
"RE-wrenches" <re-wrenches at lists.re-wrenches.org>
Date:
Friday, October 8, 2010, 9:26 PM
On 10/8/2010 6:04 PM, Matt
Lafferty wrote:
Hola Wrenches,
Does anybody know off the top of their
head if the "5-minute-wait-to-interconnect"
function is tested on 100% of inverters produced? (i.e.
every single inverter is tested with AC & DC within
the start parameters of the unit for at least 5
minutes)
Thanks!
Matt
Lafferty
Good
question. I bet it's not 100% tested because if the
software does not
change, then they may just not wait the
extra 5 minutes in order to save money on testing.
Or,
maybe they do a random sampling for this
test.
Theoretically, it shouldn't matter as long as the
software does not change
and the hardware is tested enough
in other ways, like, timers and clocks etc.
BTW,
Nowadays, there are two options for manufacturers of grid
interactive inverters....
And the UL spec has gotten
more stringent.
One option is that you have to
have the code (software) blessed by the NRTL in a
separate process (another UL specification, (UL 1998 –Software
in Programmable Components")
OR, if they don't go for
that option, then if software changes need to be done to the
inverter, the inverter must (technically) go through the
UL1741 listing process all over
again.
boB
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