20191210PAC to Staff 23-28 - Redacted.pdf

ROCKY MOUNTAIN
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December I 0, 2019
Diane Hanian
ldaho Public Utilities Commission
472 W. Washington
Boise, ID 83702-5918
d i ane. holtfatpuc. idaho. eo v (c)
RE ID PAC.E-I9-08
IPUC 4th Set Data Request (23-25)
Please find enclosed Rocky Mountain Power's Responses to IPUC 4s Set Data Requests 23-28.
Also provided is Attachment IPUC 28. Provided on the enclosed Confidential CD are
Confidential Aftachments IPUC 24-27 and Confidential Response IPUC 23. Confidential
information is provided subject to the non-disclosure agreement in this case.
Ifyou have any questions, please feel free to call me at [phone].
Sincerely,
----ls/-J. Ted Weston
Manager, Regulation
Enclosures
C.C.: Eric L. Olser/IIPA elo(nrcchohawk.com
Anthony Yankel/IIPA tony(iityankel.nct
Benjamin J. Otto/nservation.(c)
Preston N. Cartet/ orestoncarler@gi venspurlev.com
1407 W North Tample, Suite 330
salt Lake city, utah 84116
PAC-E- 19-08 / Rocky Mountain Power
Decernber 10, 2019
IPUC 3"d Set Data Request 23
IPUC Data Request 23
On page 93 of its 2019 Flexible Reserve Study (2019 IRP Volume II, Appendix
F), the Company introduces a quantile regression model for Combined Diversity
Error. For this model, please provide the following information:
(a) The model, including all regrcssion coefficients with units tbr each;
(b) If modeling data was normalized/transformed, please provide sample work
papers showing the normalization/transformation and how this was
perlormed;
(c) The standard error on each modeling coefficient;
(d) The standard error of the whole model quantile estimate;
(e) The sample quantile value (r) used in modeling, as well as an explanation of
the Company's rationale for selecting that particular quantile value;
(f) How was this formula obtained (e.g. forward regression modeling, backward
regression modeling, mixed regression modeling, or some other method); and
(g) Were interaction terms considered for inclusion in this model? Please explain
why or why not.
Confidential Response to IPUC Data Request 23
(a) For both PacifiCorp East (PACE) and for PacifiCorp West (PACW), the
model is:
Combined Diversity Error - W ind. Forecast * Wind Forecastz
* Wind Forecasts * Solar Forecast
* Solar Forecastz + Solar Forecasts
+ Load Forecast * Load Forecastz
* Load Forecast3 + NonVER Forecast
* NonVER Forecastz
PAC-E-19-08 / Rocky Morurtain Power
December 10. 2019
IPUC 3'd Set Data Request 23
Tlre rmits for the wind forecast and solar forecast variables are percentages
(forecasted outpul as a percentage of uameplate). The rmits for the load
forecast are percellages (forecasted outpul as a percentage of amual peak
load duriug the test period). The trnits for the non-variable euergy resoruce
(VER) forecast are perceutages (forecasted output as a percentage ofthe
rraxiruruu uon-\rER generatiou observed druiug the tesl period).
PAC-E- 19-08 / Rocky Mountain Power
Decernber 10, 201 9
IPUC 3'd Set Data Request 23
(b) Modeling data was not normalized or transformed.
(c) PacifiCorp did not analyze the standard errors. The model used in these
quantile regressions arises from a situation in which the relationships between
the independent variables (forecasts) and dependent variables (forecast error)
are decided before the fact in accordance with the concepts which drive
regulation reserves. For example in Figure F.3, on page 94 of the 2019
Flexible Reserve Study (FRS) - PacifiCorp's 2019 lntegrated Resource Plan
(lRP), Volume II, Appendix F - a third degree polynomial was determined to
be the best representation of the relationship between forecast and forecast
error when excluding outliers. Since these relationships ('the fit') among
variables were determined as appropriate before modeling began, there was no
need for PacifiCorp to examine 'goodness offit' statistics which seek to
provide a justification for the selection ofone model over another.
Furthermore, unlike statistical analyses in which the relationships are
unknown before the fact and the data represent a sample drawn from an
unknown population, in this case, not only are the relationships known and
defined before the fact but the data represents the population and not a random
sample.
(d) Please refer to the Company's response to subpart (c) above.
(e) As implied in the Company's response to subpart (c) above, the quantile value
is not on a sample, it's on a population. The quantile value used in the
modeling for both PACE and PACW is 0.9935. This value was chosen based
on an expectation ofachieving a loss ofload probability of 0.5 hours per year
as indicated on page 102 of the 2019 FRS - PacifiCorp's 2019 IRP, Volume
Il, Appendix F.
(g) The dependent variable is essentially net load error (deviations) where net
load is by definition load less wind less solar less non-VER. The net load error
is therefore, by definition, load error less wind error less solar error less non-
VER error. The errors on load, wind, solar and non-VER are expressed as a
function ofthe forecast as described in the Company's response to subpart (c)
above, therefore the net load srror is an additive function ofthe load forecast,
wind forecast, solar forecast and non-VER forecast. Interaction terms are not a
part of the net load error function.
Confidential information is provided subject to the non-disclosure agreement
between IPUC and the company in Case No. PAC-E-19-08.
Record holder
Sponsor:
Ramon Mitchell
Dan MacNeil
(f) Please refer to the Company's response to subpart (c) above.
PAC-E-19-08 / Rocky Mountain Power
Decernber I 0, 201 9
IPUC 3'd Set Data Request 24
IPUC Data Request 24
On pages 93 and 94 of its 2019 Flexible Reserve Study (2019 IRP Volume ll,
Appendix F), the Company states that its forecast is adjusted to achieve a
cumulative [,oss of Load Probability that corresponds to the annual reliability
target. Please provide work papers showing how this was done.
Response to IPUC Data Request 24
Please refer to Confidential Attachment IPUC 24. The model quantile value - as
referenced in the Company's response to IPUC Data Request 23 - was
continuously incremented or decremented as necessary in order to converge to the
cumulative [.oss ofLoad Probability of 0.5 hours per year. The quantile value
within the attachment of 0.9935 is the end result of multiple iterations.
Confidential information is provided subject to the non-disclosure agreement
between the company and IPUC in Case No. PAC-E-19-08.
Record holder:
Sponsor:
Ramon Mitchell
Dan MacNeil
PAC-E-19-08 / Rocky Mountain Power
December 10, 201 9
IPUC 3'd Set Data Request 25
IPUC Data Request 25
The formula for Combined Diversity Error given on page 93 of the Company's
2019 Flexible Reserve Study (2019 IRP Volume II, Appendix F) includes terms
for Wind Forecast and Solar Forecast. Were Idaho Schedule 135 net exports
included in this forecast? If not, please explain why this study should be used as a
proxy for the effects ofldaho Schedule 135 net exports. Ifso, please provide the
regression coefficients for Schedule 135 net exports, with standard errors for each
coefficient.
Response to IPUC Data Request 25
The forecasts and errors used in the Company's 2019 Flexible Reserve Study
(FRS) reflect utility-scale solar assets that existed on the Company's system
during the 2017 historical period. In that study, Idaho Schedule I 35 net exports
were not included in either the forecast or the determination of the error
associated with solar resources. Due to metering limitations, PacifiCorp does not
have an hourly forecast, actual, or error for Idaho Schedule 135 would allow for
the requested analysis.
In t}re absence ofan integration cost specific to Idaho Schedule 135 net exports,
but recognizing that these exports are typically dependent on variable energy
resources (i.e. either solar or wind), the Company's proposal includes an
integration cost based on the most comparable resource available. Since solar
power is expected to be the most common resource under the proposed schedule,
utility-scale solar integration costs reported in the Integrated Resource Plan (IRP)
were applied.
Dan MacNeil
Dan MacNeil
Record holder:
Sponsor:
PAC-E- l9-08 / Rocky Mountain Power
December 10,2019
IPUC 3'd Set Data Request 26
IPUC Data Request 26
Please provide the dates, times, and loads of the top 100 peaking events for the
calendar year 2017 .
Response to IPUC Data Request 26
Please refer to Confidential Attachment IPUC 26 for the Company's hourly actual
load and wind and solar generation for 2017. Because ofthe significant
penetration of solar resources in the Company's portfolio, it may be more
appropriate to consider the top 100 nel load hours, as shown in the attachment.
As a result of solar resources in the Company's portfolio, the Company's system
requirernents for the peak day are shifted into the evening in the 2017 historical
data.
Since 2017, additional solar resources have come online and others have been
contracted, such that solar resources under contract represent 1,759 megawatts of
nameplate capacity, which is well above the level reflected in the historical data.
The current list of contracted solar resources is listed in Table 5.6 in Volume I of
PacifiCorp's 2019 Integrated Resource Plan (lRP). Additional solar resources are
also identified as part of the 2019 IRP prefened portfolio. These additional solar
resources would further shift the Company's peak requiranents relative to the
2017 historical data.
Confidential information is provided subject to the non-disclosure agreement
between the IPUC and the company in Case No. PAC-E-19-08.
Record holder:
Sponsor:
Dan MacNeil
Dan MacNeil
PAC-E-I9-08 / Rocky Mountain Power
Decernber 10, 2019
IPUC 3'd Set Data Request 27
IPUC Data Rcquest 27
Please provide the results ofall loss ofLoad Probability studies related to the
avoided capacity value of Schedule 135 net exports.
Response to IPUC Data Request 27
Please refer to Confidential Attachment IPUC 27 for a calculation ofthe capacity
contribution associated with the exported energy from a census ofresidential Utah
solar customers in climate region 68, which encompasses northem Utah. The
Company's Idaho service territory is also predominantly in climate zone 68.
These result represent the most comparable hourly export data available.
Note: PacifiCorp's 2019 lntegrated Resource Plan (IRP) capacity contribution
analysis incorporates the correlation between resources across the Company's
system. As a resu'lt, the capacity contribution ofvariable resources whose output
is correlated with existing assets in the Company's portfolio is reduced. The
Company has estimated this effect for the proxy wind and solar resources
available for selection in the 2019 IRP, but has not specifically identified a value
for a net export profile, which is expected to reflect variations in both resource
output and load.
Confidential inflormation is provided subject to the non-disclosure agreement
between IPUC and the company in Case No. PAC-E-19-08.
Record holder:
Sponsor:
Dan MacNeil
l)an MacNeil
PAC-E- l9-08 / Rocky Mountain Power
December 10,2019
IPUC 3'd Set Data Request 28
IPUC Data Request 28
The Company proposes that the transition period would only apply to residential
customers. Please provide an estimate of the annual financial impact for each
Idaho Schedule 135 non-residential customer.
Response to IPUC Data Request 28
For alternative transition plan, the Company recommends that the same transition
timing and export credit transition logic be applied to Residential and Schedule 23
customer generators. The Company recommends that there be no transition for
Schedule 6 customer generators and any other schedule that may interconnect
customer generation in the future. Existing Schedule 6 customer generators would
be subject to the Net Billing program effective February I ,2020 and would be
credited for their exported energy at the Company's proposed cost-based prices.
Please refer to Company witness, Robert M. Meredith's direct testimony for the
detailed proposals and recommendations.
Please refer to Attachment IPUC 28 for the estimated average annual financial
impact for each ldaho Schedule 135 non-residential customer based on the
Company' s recommendalions.
Record holder
Sponsor:
James Zhang
Robert Meredith