FPL TRMID

Revision 1

Date: 1/11/12

FPL Transmission Reliability Margin Implementation Document

Revision History

Rev / Changes / Author / Approver / Date
0 / Initial Draft / JCR/DAM / DAM / 3/24/11
1 / Modifications to section 2 B. Minor changes elsewhere. / AJA/DAM / DAM / 1/11/12


Transmission Reliability Margin Implementation Document (TRMID)

I.  Introduction

A.  Background

Florida Power and Light (FPL), as a Transmission Operator, chooses to maintain a Transmission Reliability Margin (TRM) as permitted by the NERC MOD standards (MOD-008 and MOD-028).

B.  Purpose

This document serves as FPL’s TRMID and explains the methodology utilized by FPL to calculate and use TRM for its transmission system operations.

II.  TRM Calculation (MOD-008 R1, R2)

A.  General

FPL uses two different components of uncertainty for individual ATC paths. The first component allows for a difference between short-term and continuous facility ratings and the corresponding operator response. The second component accounts for variations in generation dispatch and is applied only in the time interval beyond seven days.

FPL’s paths involving the Southern sub-region have a contractual as well as a physical limitation. The application of TRM on paths where Southern is the point of receipt is described in section C of this document.

B.  TRM Components (Mod-008 R1.1, R1.2)

FPL uses the following two components in its TRM calculation.

Short-term System Operator Response (TTC Calculator component)

For the calculation of Total Transfer Capability (TTC), short-term facility ratings may be higher than the continuous ratings and reflect System Operating Limits (SOL) which have time restrictions. The Short-term System Operator Response component is the difference between the TTC calculation using the short-term facility ratings and TTC calculation using the continuous facility ratings.

Since these SOL are time dependent and System Operators have the option to curtail non-firm transactions as a mitigation measure, this component is used to prevent this higher capacity from being used for firm transactions which cannot be curtailed.

This component of TRM is determined for each individual ATC path each time TTC is calculated, and is applicable only if the limiting facility has a difference in short-term and continuous ratings.

Variations in Generation Dispatch (Critical Unit Offline)

The second component of TRM is meant to reflect the uncertainty in generation dispatch in the longer-term time intervals; specifically forced or unplanned outages of a unit that has a significant impact on Available Transfer Capability. This TRM is only applied to firm ATC and only after day seven.

The generation uncertainty component of TRM is developed from the FRCC Transmission Working group topology model used for the TTC calculations. A First Contingency Incremental Transfer Capability (FCITC) is determined (according to MOD-28 R6.1 & R6.2) for the base model and a series of models with different critical generating units offline. The TRM per path is the difference between the lowest FCITC with a critical unit off and the base FCITC.

This component of TRM is used on all posted ATC paths. The calculations are done on an individual path basis so the allocation is 100% on that path.

C.  TRM as Applied to the Southern Paths

The TTC on FPL’s Southern paths is the lower of FPL’s contractual allocation or the calculated TTC limit for the specific path. For the calculated TTC limit the TRM components described above are applied. For the contractual allocation a TRM based on the L10 control performance metric (BAL-001-0.1a R2) is used. This TRM applies only to the contractual allocation and only on paths where Southern is the point of receipt. The TRM on these paths is described in further detail in the “TTC Methodology for the Southern Interface”. This contractual TRM is released as non-firm for all horizons.

D.  TRM Use and Calculation Frequencies (MOD-008 R1.3,R4,R5)

Same Day and Real-Time (Scheduling Horizon)

For the above horizon only the Short-term System Operator Response component of TRM is applied.

Day-Ahead and Pre-Schedule (Operating Horizon)

For the above horizon, only the Short-term System Operator Response component of TRM is applied.

Beyond Day-Ahead and Pre-Schedule, to Thirteen Months (Planning Horizon)

For the day-ahead out to seven days, only the Short-term System Operator Response component of TRM is applied.

From day eight out to month thirteen the TRM applied is equal to the sum of the Short-term System Operator Response component and the Variations in Generation Dispatch component based on a critical unit offline.

Calculation Frequencies

The Short-term System Operator Response component of TRM is determined every time TTC is calculated which is hourly for the next 72 hours, daily for hours 73 – 168, and weekly for day 8 through month 13. This TRM component is immediately included in the ATC equation upon calculation.

The Variations in Generation Dispatch component of TRM is calculated by FPL once per year.

E.  TRM Communication (MOD-008 R3, R5)

FPL functions as a Transmission Provider and Transmission Planner as well as a Transmission Operator. It communicates its TRM values through the posting of these values to the online reservation evaluation software to which the above entities have access.

This TRMID is posted on FPL’s public OASIS website, the site for FRCC Operating Entities, and will be provided, along with any underlying documentation, within 30 days of a request by any of the following entities: Transmission Service Providers, Reliability Coordinators, Planning Coordinators, Transmission Planners, and Transmission Operators.

FRCC Operating Entities Posting Area- BAs/TOPs

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