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Transmission and Distribution Losses

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Transmission and Distribution Losses

ERCOT Protocols

Section 13: Transmission and Distribution Losses

January 1, 2009

    ABLE OF CONTENTS: SECTION 13 TRANSMISSION AND DISTRIBUTION LOSSES T

    13 Transmission and Distribution Losses ............................................................................... 13-1

    13.1 Overview .........................................................................................................................................13-1

    13.2 Transmission Losses ........................................................................................................................13-2

    13.3 Distribution Losses ..........................................................................................................................13-4

    13.4 Special Loss Calculations for Settlement and Analysis ...................................................................13-5 ERCOT PROTOCOLS JANUARY 1, 2009

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    SECTION 13 TRANSMISSION AND DISTRIBUTION LOSSES

    13 TRANSMISSION AND DISTRIBUTION LOSSES

    13.1 Overview

    This section sets forth the method for calculating Transmission and Distribution Losses (T&D Losses) and responsibilities of ERCOT, Qualified Scheduling Entities (QSEs), and Transmission and/or Distribution Service Providers (TDSP) with respect to T&D Losses.

    13.1.1 Responsibility for Transmission and Distribution Losses

    T&D Losses are the responsibility of the QSE representing the Competitive Retailer’s Load.

    The QSE will schedule the necessary amount of energy to cover Competitive Retailer’s Load plus the applicable T&D Losses. ERCOT shall allocate T&D Losses to Load at the appropriate aggregate level as part of the data aggregation process to calculate the Load obligation of QSEs for settlement purposes.

    Transmission Loss Factors shall be forecasted by ERCOT, and posted to the MIS by 0600 of the Day Ahead period. ERCOT shall forecast the ERCOT-wide Transmission Loss Factors expressed as a percent of Load for each settlement interval of the Operating Day. On the day following the Operating Day, ERCOT shall also calculate Transmission Loss Factors for each Settlement Interval using actual ERCOT System Load for that Settlement Interval and will post the resulting deemed actual Transmission Loss Factors to the settlement system and the MIS. Distribution Loss Factors (DLF)shall be forecasted by ERCOT, and posted to the MIS by 0600 of the Day Ahead period. ERCOT shall forecast the DLFs expressed as a percent of Load for each Settlement Interval of the Operating Day.

    On the day following the Operating Day, ERCOT shall also calculate DLFs for each Settlement Interval using actual ERCOT System Load for that Settlement Interval and post the resulting deemed actual DLFs to the settlement system and the MIS.

    DLFs will be subject to audit by ERCOT for accurate and consistent application. Non-Opt-in Entities (NOIE) with Interval Data Recorders at the settlement point of delivery are not required to provide DLFs.

    In the special case where there are distribution Facilities upstream from a wholesale NOIE settlement IDR that settlement IDR will be compensated for line and transformer losses between the IDR and the ERCOT Transmission Grid to account for the Distribution Losses. The NOIE will be then treated as a transmission level NOIE. Calculations are subject to review by ERCOT. Since loss compensation is included in the wholesale settlement IDR, the TDSP providing upstream wheeling facilities may need to offer wholesale wheeling tariffs excluding the losses that have already been compensated for.

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    SECTION 13 TRANSMISSION AND DISTRIBUTION LOSSES

    13.1.2 Calculation of Losses for Settlement

    ERCOT shall use the deemed actual DLFs applicable to each ESI ID and the deemed actual Transmission Loss Factors when adjusting aggregated Load for losses to determine the QSE total Load obligations.

    13.2 Transmission Losses

    13.2.1 Forecasted Transmission Loss Factors

    The forecasted Transmission Loss Factor for each interval in the Operating Day shall be a linear interpolation or extrapolation using the on-peak and the off-peak Transmission Loss Factors and the corresponding forecast of ERCOT System Load during the same interval to calculate the loss factors.

    At 0600 of the Day Ahead period, ERCOT shall forecast a Transmission Loss Factor for each Settlement Interval of the Operating Day and post the forecasted Transmission Loss Factors which correspond to the Operating Day forecast. The source of the on-peak and off-peak losses are the ERCOT load flow base cases for the applicable season.

    13.2.2 Deemed Actual Transmission Loss Factors

    ERCOT will determine the deemed actual Transmission Loss Factor for each interval in the Operating Day, by use of a linear interpolation or extrapolation using the on-peak and the off-peak Transmission Loss Factors corresponding to the actual ERCOT System Load for the interval.

    The day after the Operating Day, ERCOT shall calculate deemed actual Transmission Loss Factors for each Settlement Interval of the Operating Day and post the Transmission Loss Factors to be used in settlement calculations.

    ERCOT shall use the Transmission Loss Factors corresponding to the on-peak and off-peak base case ERCOT System Loads during the applicable seasons as the basis for the ERCOT-wide deemed actual Transmission Loss Factors. ERCOT will post Transmission Loss Factors to the MIS by 0600 two (2) days after the Operating Day.

    13.2.3 Transmission Loss Factor Calculations

    The following formulas shall be used to translate the seasonal on-peak and off-peak Transmission Loss factors into Settlement Interval Transmission Loss Factors.

    TLF

     = (SSC * SIEL) + SIC ii

    Where:

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    i = interval

    TLF = Transmission Loss factors for a settlement interval i

    SIEL = Settlement Interval ERCOT System Load (forecasted or actual) i

    SSC = Seasonal Slope Coefficient

    SIC = Seasonal Intercept Coefficient

    And,

    SSC = (SONLF SOFFLF)/(SONL-SOFFL)

    SIC = [(SOFFLF*SONL)-(SONLF*SOFFL)]/(SONL-SOFFL)

    Where:

    SONLF = Seasonal on-peak percent loss factor

    SOFFLF = Seasonal off-peak percent loss factor

    SONL = Seasonal on-peak Load value

    SOFFL = Seasonal off-peak Load value

    13.2.4 Seasonal Transmission Loss Factor Calculation

    Seasonal on-peak and off-peak Transmission Loss Factors are derived from annually updated

    ERCOT on-peak and off-peak load flow base cases analysis by ERCOT. Base cases reflect the

    most current data on the transmission system and Generation Resource dispatch. The ERCOT

    Transmission Grid topology and related Generation Resource dispatch in the base cases are the

    critical factors in calculating losses. Seasonal time periods are defined as follows:

    (1) Spring (March May)

    (2) Summer (June August)

    (3) Fall (September November)

    (4) Winter (December February) ERCOT shall calculate seasonal Transmission Loss Factors by dividing ERCOT seasonal case

    transmission losses (60 kV system and higher) by ERCOT seasonal base Load adjusted (reduced)

    for self serve Load modeled in the case. The resulting loss factors are expressed as a percentage

    of Load.

    ERCOT shall post, to the MIS, seasonal Transmission Loss Factors thirty (30) days prior to the

    start of the season.

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    13.2.5 Loss Monitoring

    ERCOT shall monitor Transmission Losses annually and will investigate abnormal loss factors.

    ERCOT and Transmission Service Providers shall use the cost of losses as one criterion in

    evaluating the need for transmission additions.

    13.3 Distribution Losses

    By October 30th of each year for the next calendar year, or two (2) months prior to the posting of

    any update to the approved Distribution Loss Factor (DLF) codes and calculation each

    Distribution Service Provider (DSP), except NOIEs, shall calculate and provide ERCOT the

    Annual DLFs to be applied to distribution voltage level Loads in its area of certification.

    ERCOT shall review and approve the DLF calculation methodology used by each DSP prior to

    use of the loss factors for settlement purposes. If the DLF calculation methodology does not

    conform with ERCOT’s interpretation of the Protocol criteria in this subsection, ERCOT will

    work with the DSP to correct the deficiency. Until deficiencies are resolved, the last approved

    DLF and the calculation methodology will be posted, and the last approved DLFs shall be used

    for settlement. A DSP may only submit a change to the DLF calculation methodology annually

    or when a change in a DSP service area warrants an update to the approved DLF based on the

    DSP internal evaluation.

The TDSP shall assign a DLF code to each ESI ID. A maximum of five (5) DLFs may be

    submitted for each DSP based upon ERCOT approved parameters, such as service voltages or

    number of transformations.

    The following coding standards will be used to identify the DLF applicable to each ESI ID:

    ? T = Transmission connected Customers (no Distribution Loss Factor applied)

    ? A through E = TDSP defined Customer segment(s)

    The DSPs, except NOIEs, are obligated to provide DLFs to ERCOT. ERCOT will post the DLF

    and calculation methodology, including any equations and constants, for each DSP.

    Loss factor variables submitted by the DSP shall include:

    (1) The annual DLF coefficients (F

    , F, and F) for each DLF code; and 123

    (2) The methodology upon which the calculation of the coefficients (F, F, and F) was 123

    made.

    13.3.1 Loss Factor Calculation

    ERCOT shall use the DLFs submitted by the DSP to calculate the Settlement Interval DLFs.

    DLFs will be calculated from the data provided by DSPs as follows using the following equation:

    SILF = F * (SIEL/AAL) + F + F / (SIEL/AAL) i1i23i

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    Where:

    i = interval

    SILF = Settlement Interval DLF i

    SIEL = Settlement Interval ERCOT System Load (forecasted or actual) i

    AAL = Annual Interval Average ERCOT System Load (forecasted or actual)

    FFF= Coefficients determined by the DSP to allow calculation of its SILF from 1 , 2 , 3

    ERCOT System Load

    ERCOT shall use the deemed actual DLFs calculated for each Settlement Interval of the

    Operating Day for settlement purposes.

    13.3.2 Loss Monitoring

    DLFs for all Distribution Service Providers, except for NOIEs, will be submitted to ERCOT and

    will be subject to audit for accuracy and consistency of application.

    13.4 Special Loss Calculations for Settlement and Analysis

    13.4.1 Deemed Actual Transmission Losses for NOIEs

    All QSEs representing Load, including NOIEs, will be responsible for Transmission Losses

    allocated in the manner described in these Protocols. Those Entities using transmission tie line

    meters to determine Load will adjust the net meter readings to remove calculated Transmission

    Losses behind the meter in order to determine the Load responsibility of the Entity. ERCOT will

    provide to settlement the calculation of the losses behind the meters, for each interval, using

    actual system conditions for that interval.

    The deemed actual Transmission Losses for NOIEs shall be a linear interpolation or

    extrapolation between the seasonal on-peak and the seasonal off-peak NOIE Transmission Loss

    Factors corresponding to the actual NOIE system Load in the interval.

    ERCOT shall calculate seasonal NOIE Transmission Loss Factors corresponding to the on-peak

    and off-peak base case NOIE system Loads during each of the four (4) seasons of the upcoming

    year as the basis for the NOIE Transmission Loss Factors. NOIE seasonal loss factors will be

    calculated in the same manner as the loss factors are calculated for the ERCOT wide

    Transmission Loss Factors.

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