Inverter Meter Spec - Revised

[Baumstark, Pete]

Attached is the revised version of the inverter meter spec.  The revisions are based on our review meeting last week.  Please let me know if I'm missing anything.

 

Thank you,

Pete Baumstark

KEMA, Inc.

[Stephey, Harry]

Pete:

 

Have you received any feedback on this?

 

Harry

---

From: onboard...@googlegroups.com [mailto:onboard...@googlegroups.com] On Behalf Of Baumstark, Pete
Sent: Friday, March 13, 2009 12:11 AM
To: onboard...@googlegroups.com
Subject: {CSI 5 Meters} Inverter Meter Spec - Revised

[Baumstark, Pete]

I haven't gotten any comments at all

________________________________

[Chaset, Nicolas L.]

5% metering accuracy group-

 

First let me extend my thanks to to Matt Lafferty and Pete Baumstark for all the work they have both done to move this standard forward.  As things currently stand, we are very close to having a completed testing specification and there is now one last opportunity to provide comment before the specification is finalized.  All interested parties should review the draft document that Matt Lafferty sent out last week and provide comment to Pete Baumstark (pete.ba...@kema.com) no later than one week from today (March 25, 2009).  The CPUC and the California Solar Initiative Program Administrators may hold a future workshop to discuss implementation of the 5% metering accuracy standard, but not timeline has be developed for that as yet.

 

Thank you all for your collaboration. 

 

 

Nicolas Chaset

California Solar Initiative

California Public Utilities Commission

415-703-1184

n...@cpuc.ca.gov

[Matt Lafferty]

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[Marv Dargatz]

My comments to the 5% metering accuracy draft follow.

We have real heartache with only one test. Test #2, Load Performance
would be difficult, if not impossible to pass. Some laboratory meters
would even have some difficulty meeting the requirements at the 10%
power level. Test #5, Effect of Internal Heating is a bit unclear.

Test#2, Load Performance
Essentially, as written, the test requires a built-in meter with a 0.5%
full scale accuracy. I would like to offer a prudent and reasonable
solution. There are two parts to this:

1. Run the test as described. Apply the Weighted Accuracy formula as
was described in the marked out equation 4-2, except delete the first
term, as we do not do efficiency tests at the 5% power level. Apply the
CEC weighting factors of Power/Weight; 10%/4%, 20%/5%, 30%/12%, 50%/21%,
75%/53%, 100%/5%. Then, change the Pass/Fail criteria to read "The
weighted accuracy as calculated by formula 4-2 must be in the range of
+/-5%."

2. Our intent is to run the meter tests in conjunction with other tests
which are already being performed, as much as possible. We do not
perform the tests in rows D and E of table 4-1. We should, however,
verify the meter accuracy at ac voltages other than nominal. I would
suggest that we grey out the boxes in 10%, 20%, 30%, 50%, and 75% in
rows D, change the Vdc to Vnom, and delete row E. The test to verify
meter accuracy at low and high line voltage shall be performed at 100%
power only. So, this test essentially integrates Test #3, Effect of
Variation of Voltage.

Test #5, Effect of Internal Heating
I would propose that we perform this test during the CEC maximum
continuous power test. This involves 150 minutes of maximum power at
40c. Pass/Fail would be that the meter accuracy is within 5% as defined
by equation 4.1 at the end of the 150 minute test. We might also
consider a maximum deviation from the result of the 100% power test in
Test #2 of 2.5%.

Test #7, Independence of Elements
Let's clarify that a split-phase system is not considered multi-phase.
Grid Interactive inverters should have no problem with this test, as
they are required to cease exportation of power upon loss of phase.
Maybe a definition is section 2.1. "Multi-phase units: an inverter
which exports power on more than 2 conductors."

Test #11, Effect of Variation of Ambient Temperature
Seems like we should be able to combine Test #5, Effect of Internal
Heating and Test #11, Effect of Variation of Ambient Temperature into
one test. By starting the test at the lowest temperature, the total
test time is less. Also, if we change the power levels to 50% and 100%
we can cut this test time in half, and allow integration with the
standard UL1741, section 43 temperature test. In fact, Test #3, Effect
of Variation of Voltage can be run at this time, as we already run the
four corners of DC and ac voltage combinations during the temperature
test. If minimum storage and operating temperatures are the same, Test
#17, Effect of Operating Temperature can be run prior to running Test
#11, but with the same equipment setup.

Comments welcome!

See Ya!

Marv
Enphase Energy
707 763-4784 x7016

Chaset, Nicolas L. wrote:
> 5% metering accuracy group-
>
> First let me extend my thanks to to Matt Lafferty and Pete Baumstark for
> all the work they have both done to move this standard forward. As
> things currently stand, we are very close to having a completed testing
> specification and there is now one last opportunity to provide comment
> before the specification is finalized. All interested parties should
> review the draft document that Matt Lafferty sent out last week and
> provide comment to Pete Baumstark (pete.ba...@kema.com

> <mailto:pete.ba...@kema.com>) no later than one week from today

> (March 25, 2009). The CPUC and the California Solar Initiative Program
> Administrators may hold a future workshop to discuss implementation of
> the 5% metering accuracy standard, but not timeline has be developed for
> that as yet.
>
> Thank you all for your collaboration.
>
>
> Nicolas Chaset
> California Solar Initiative
> California Public Utilities Commission
> 415-703-1184

> n...@cpuc.ca.gov <mailto:n...@cpuc.ca.gov>
>
> >

[Baumstark, Pete]

See my responses below.

Thank you,
Pete

RESPONSE: I don't have a problem with doing this. That's somewhat how I
had originally written it. I WILL CHANGE IT IF THERE ARE NO OBJECTIONS.

2. Our intent is to run the meter tests in conjunction with other tests

which are already being performed, as much as possible. We do not
perform the tests in rows D and E of table 4-1. We should, however,
verify the meter accuracy at ac voltages other than nominal. I would
suggest that we grey out the boxes in 10%, 20%, 30%, 50%, and 75% in
rows D, change the Vdc to Vnom, and delete row E. The test to verify
meter accuracy at low and high line voltage shall be performed at 100%
power only. So, this test essentially integrates Test #3, Effect of
Variation of Voltage.

RESPONSE: I have no problem with taking out D & E all together, if that
is the consensus of the working group. I don't think it's appropriate
at this time to try and combine the load performance test with the high
and low voltage test - at least not within the text of this
specification. During actual testing, any of these tests can be
combined with other tests, as long as the stated requirements are met.
UNLESS ANYONE DISAGREES, I'LL REMOVE THE D & E STEPS OF TEST NO. 2.

Test #5, Effect of Internal Heating
I would propose that we perform this test during the CEC maximum
continuous power test. This involves 150 minutes of maximum power at
40c. Pass/Fail would be that the meter accuracy is within 5% as defined

by equation 4.1 at the end of the 150 minute test. We might also
consider a maximum deviation from the result of the 100% power test in
Test #2 of 2.5%.

RESPONSE: Test No. 5 is run at 23 deg C ambient. The Max Continuous
Output Power test is run near the manufacturer's rated maximum
temperature. UNLESS THERE'S ANY DISAGREEMENT, I WILL MAKE NO CHANGE TO
TEST NO. 5.

Test #7, Independence of Elements
Let's clarify that a split-phase system is not considered multi-phase.
Grid Interactive inverters should have no problem with this test, as
they are required to cease exportation of power upon loss of phase.
Maybe a definition is section 2.1. "Multi-phase units: an inverter
which exports power on more than 2 conductors."

RESPONSE: I WILL INCLUDE THIS DEFINITION IN BOTH SECTION 2.1 AND WITHIN
THE TEXT OF TEST NO. 7.

Test #11, Effect of Variation of Ambient Temperature
Seems like we should be able to combine Test #5, Effect of Internal
Heating and Test #11, Effect of Variation of Ambient Temperature into
one test. By starting the test at the lowest temperature, the total
test time is less. Also, if we change the power levels to 50% and 100%
we can cut this test time in half, and allow integration with the
standard UL1741, section 43 temperature test. In fact, Test #3, Effect
of Variation of Voltage can be run at this time, as we already run the
four corners of DC and ac voltage combinations during the temperature
test. If minimum storage and operating temperatures are the same, Test
#17, Effect of Operating Temperature can be run prior to running Test
#11, but with the same equipment setup.

RESPONSE: These are all good comments. What would really be required
would be to make up a matrix showing each test, the power levels run,
the durations, the ambient temperatures, the number of cycles through,
etc. Included in the matrix would be requirements from the source specs
(IEEE 1547.1, UL1741, ANSI C12.1). In such a way synergies could be
developed between the various tests, resulting in limiting the actual
number of tests. Also keep in mind that any of these tests can be
combined with other tests when actual test procedures are developed by
the NRTL (in conjunction with the manufacturer) as long as none of the
requirements for each test are compromised. It would probably be better
to go through some sample testing in this fashion to fully flush out any
"tweaks" that could be made to reduce test time and propose those
changes to the working group. I FEEL IT'S BEYOND THE SCOPE OF THIS
EFFORT FOR THE INITIAL RELEASE TO DEVELOP MATRICIES TO TRY AND FLUSH OUT
SYNERGIES AND POTENTIALLY COMBINE TESTS. IT'S ALSO BEYOND THE SCOPE TO
WORK WITH ONE OR MORE NRTLS/MANUFACTURERS IN RUNNING THROUGH INITIAL
TEST PROCEDURES FOR THE PURPOSE OF STREAMLINING THE SPECIFICATION.
THESE MODIFICATIONS CAN BE TAKEN AS ACTIONS FOR THE 5% WORKING GROUP. I
WILL PROPOSE TO NOT MAKE CHANGES TO THE TESTS AS SUGGESTED IN THE ABOVE
PARAGRAPH.