Cleco Power LLC
FERC Electric Tariff, Third Revised Volume No. 1
First Revised Sheet No. 95
ATTACHMENT C
Methodology to Assess Available Transfer Capability
1.0 General
This attachment describes Cleco’s algorithms, flowchart, and methodology for determination of
Available Transfer Capability (ATC). The methodology is based on the June 1996 approved
reference document published by the North American Electric Reliability Council entitled
“Available Transfer Capability Definitions and Determination” as a framework for determining
Available Transfer Capability (ATC) to satisfy both Federal Energy Regulatory Commission
(FERC) requirements and industry needs.
2.0 Methodology
Cleco’s primary methodology for calculating ATC employs a flow-based methodology which is
commonly referred to by FERC as network ATC. This calculation takes into account flow based
limits based upon the lesser of thermal capability of the network, voltage stability, and/or
transient stability. However, there are exceptions for interfaces where Cleco administers a
contract path limit. In these instances, the ATC will be the lesser of the calculated network ATC
or contract Path.
3.0 Definitions
The North American Electric Reliability Corporation (NERC) provides the following definitions
in the “Glossary of Terms Used in Reliability Standards” (updated May 2, 2007, available at:
ftp://www.nerc.com/pub/sys/all_updl/standards/rs/Glossary_02May07.pdf):
3.1 Total Transfer Capability (TTC) is the amount of electric power that can be moved or
transferred reliably from one area to another area of the interconnected transmission systems by
way of all transmission lines (or paths) between those areas under specified system conditions.
3.2 Available Transfer Capability (ATC) is a measure of the transfer capability remaining in the
physical transmission network for further commercial activity over and above already committed
uses. It is defined as Total Transfer Capability less existing transmission commitments
(including retail customer service), less a Capacity Benefit Margin, less a Transmission
Reliability Margin.
3.3 Firm Transmission Service is the highest quality (priority) service offered to customers under
a filed rate schedule that anticipates no planned interruption.
3.4 Non-Firm Transmission Service is transmission service that is reserved on an as-available
basis and is subject to curtailment or interruption
3.5 Transmission Reliability Margin (TRM) is the amount of transmission transfer capability
reserved to provide for reliable operation of the transmission system. TRM is calculated yearly
Issued by: Cynthia B. Guillot, Director Transmission Policy & Contracts
Issued on: September 10, 2007
Effective on: September 11, 2007
Cleco Power LLC
FERC Electric Tariff, Third Revised Volume No. 1
First Revised Sheet No. 96
for the Planning Horizon unless modifications to the transmission grid would necessitate a
recalculation of TRM for a specific path. TRM is based on the flow based amount of power that
must be reserved for each flowgate to allow generation from each Control Area within the
Reserve Sharing Group to deliver its allocation of power.
3.6 Capacity Benefit Margin (CBM) is the amount of firm transmission transfer capability
preserved for Load Serving Entities (LSEs) on the host transmission system where their load is
located, to enable access to generation from interconnected systems to meet generation reliability
requirements. Preservation of CBM for a LSE allows that entity to reduce its installed
generating capacity below that which may otherwise have been necessary without
interconnections to meet its generation reliability requirements. The transmission capacity
preserved as CBM is intended to be used by the LSE only in times of emergency generation
deficiencies.
4.0 Algorithm for ATC Determination
4.1 Power Flow Models
Cleco develops daily, weekly, and monthly power flow models for calculation and posting of
available transfer capabilities. These base case models include load forecast data, generation
dispatch, approved outages (transmission and generation), open access transactions (point to
point and network) based on the appropriate calculation horizon as well as pre-Order 888
grandfathered contracts. In addition to modeling requirements within the Cleco control area,
power flow data described above is exchanged and coordinated with interconnecting neighbors.
4.1.1 Hourly Base Case Power Flow Models
Cleco does not develop hourly power flow models for calculation of transfer capabilities.
Hourly transfer capabilities are based on the results of each daily transfer capability
simulation using daily power flow models described below. Twenty-four (24) hours of
transfer capabilities are posted based on results of the daily peak hour for at least seven
(7) days into the future from the current operating day.
4.1.2 Daily Base Case Power Flow Models
Cleco develops daily power flow models for calculation and posting of transfer
capabilities at a minimum of thirty-one (31) days into the future from the current
operating day. These models include 1) Cleco’s forecasted daily peak for native load,
2) generation which is economically dispatched to serve peak forecasted load including
both generation owned by native load as well as units declared as designated network
resources (DNRs) through purchased power contracts, 3) approved transmission and
generation outages, and 4) firm and non-firm open access transactions (point-to-point and
network) based on the appropriate calculation horizon as well as pre-Order 888
grandfathered contracts.
Issued by: Cynthia B. Guillot, Director Transmission Policy & Contracts
Issued on: September 10, 2007
Effective on: September 11, 2007
Cleco Power LLC
FERC Electric Tariff, Third Revised Volume No. 1
Original Sheet No. 96A
4.1.3 Weekly Base Case Power Flow Models
Cleco develops weekly models to calculate and post transfer capabilities at a minimum of
eight (8) weeks into the future from the current operating week. These models include
1) Cleco’s forecasted weekly peak for native load, 2) generation which is economically
dispatched to serve peak load including both generation owned by native load as well as
units declared as DNRs through purchased power contracts, 3) approved transmission and
generation outages, and 4) firm open access transactions (point-to-point and network)
based on the planning horizon as well as pre-Order 888 grandfathered contracts.
4.1.4 Monthly Base Case Power Flow Models
Cleco calculates and posts transfer capabilities up to thirteen (13) months into the future
from the current operating month. The models are based on seasonal SPP models and
include 1) Cleco’s forecasted seasonal peak load for native load, 2) generation which is
economically dispatched to serve peak load including both generation owned by native
load as well as units declared as DNRs through purchased power contracts, 3) approved
transmission and generation outages, and 4) firm open access transactions (point-to-point
and network) based on the planning horizon as well as pre-Order 888 grandfathered
contracts.
4.1.5 Yearly Base Case Power Flow Models
Cleco participates in the SPP annual model development and models are developed up to
ten (10) years into the future based on Model Development Working Group (MDWG)
input. Cleco’s input into the model is based on forecasted annual peak load, generation
which is economically dispatched to serve forecasted load including both generation
owned by native load as well as units declared as designated network resources (DNR)
through purchased power contracts, and firm open access transactions (point-to-point and
network) based on the planning horizon as well as pre-order 888 grandfathered contracts.
Rollover rights are assumed on firm transmission contracts with duration of five years or
greater. Cleco does not calculate or post yearly TTC and/or ATC since Long Term Firm
(LTF) transmission requests are not granted without a System Impact Study (SIS).
4.2 Transfer Capability Methodology
Cleco utilizes a flow-based network ATC methodology to calculate transfer capabilities with its
first tier neighbors. Cleco recognizes constraints and limitations both internal and external to the
Cleco transmission system. The ATC values that Cleco calculates and posts on OASIS are equal
to the First Contingency Incremental Transfer capabilities (FCITC) which is the output derived
from the power flow simulation of transfers. Total Transfer Capability (TTC) values are derived
from ATC plus existing transmission commitments (ETC). ETC is the amount of confirmed
transmission capacity on Cleco’s OASIS (point-to-point and network) including native load as
well as transmission capacity committed under pre-Order 888 grandfathered contracts.
Issued by: Cynthia B. Guillot, Director Transmission Policy & Contracts
Issued on: September 10, 2007
Effective on: September 11, 2007
Cleco Power LLC
FERC Electric Tariff, Third Revised Volume No. 1
Original Sheet No. 96B
Transfers are simulated simultaneously with ETCs into and out of Cleco for each path on a nonsimultaneous basis. A transfer test level is simulated by increasing generation in the sending
control area such that generation does not exceed the maximum MW output of each unit, while
simultaneously decreasing generation in the receiving control area such that generation does not
drop below the minimum MW capability of unit. The transfer test level is set for each path
either in excess of the thermal capability of the interconnected system or equal to the contract
path limits, whichever is greater.
The network ATC is calculated by monitoring and outaging facilities declared by each first tier
Transmission Provider as flowgates, for calculation of the most limiting system element for each
transfer. For paths in which a contract path limit exists, the lesser of the network available
transfer capability or contract path limit is deemed to be the amount of available transfer
capability.
4.2.1 Transmission Reliability Margin (TRM)
Cleco participates in the SPP generation reserve sharing program. TRM is calculated at
least annually for each season based on the flow impact on transmission facilities during
the implementation of the reserve sharing process. Cleco determines it’s TRM for each
path by simulating the loss of individual generators with replacement power modeled as a
call for generation reserve sharing via power flow analyses. The increased flow on the
most limiting element during reserve sharing implementation becomes the TRM for that
interface. Cleco does not withhold transmission capacity in terms of TRM for any
inaccuracies associated with the power flow model including load forecast errors,
forecast errors in system topology or distribution factors and loop flow sources.
4.2.2 Capacity Benefit Margin (CBM)
Cleco evaluates and determines its CBM requirements at least annually. Currently, Cleco
does not withhold ATC in terms of CBM to meet the SPP planning requirements, due to
the ownership of native load generation and execution of purchase power agreements
(PPAs) as opposed to withholding transmission capacity in terms of CBM.
4.2.3 Software and Databases used in Posting Transfer Capabilities
Cleco uses industry accepted software (Siemens PSSE/MUST) to calculate transfer
capabilities. The results from MUST are downloaded into a spreadsheet
(TTC_AUTOMATION2.xls) for uploading into an access database (Tracking.mdb). This
access database interacts with OASIS to retrieve and update OASIS requests as well as
upload TTC and ATC to OASIS. This database is also used for Cleco’s internal
validation program for checking all transmission service request information including
ATC.
Issued by: Cynthia B. Guillot, Director Transmission Policy & Contracts
Issued on: September 10, 2007
Effective on: September 11, 2007
Cleco Power LLC
FERC Electric Tariff, Third Revised Volume No. 1
Original Sheet No. 96C
4.2.4 Frequency of Updating Transfer Capabilities
Calculations of TTC and ATC are performed and updated daily on Cleco’s OASIS.
ATCs are updated more frequently than TTC, since ATC is updated as both firm and
non-firm transmission service requests are granted on OASIS.
5.0 Calculations for the Scheduling Horizon
This period is the defined as same-day and real time.
Firm Available Transfer Capability (Firm ATC) is not available during scheduling horizon due
to timing requirements in the Open Access Transmission Tariff (OATT).
Non-Firm Available Transfer Capability (Non-Firm ATC) is the remaining capacity available for
additional non-firm transmission reservations after the committed uses for firm reservations have
been scheduled and existing non-firm reservations have been subtracted from TTC. Firm
transmission reservations are not used in the Scheduling Horizon or any part of the real time day
for calculation of non-firm ATC.
Non-Firm ATC = TTC – CBM – TRM – Existing Firm Transmission Commitments Scheduled
– Existing Non-Firm Transmission Commitments
Existing Firm Transmission Commitments Scheduled includes:
 Energy schedules of firm reservations in the scheduling horizon
6.0 Calculations for the Operating Horizon
This period is the defined as day ahead and prescheduled.
During pre-scheduling of firm transmission service, estimates of firm transmission reservations
are included in the firm and non-firm ATC calculation to set-aside capacity in the absence of
approved E-Tags/schedules and ancillary service sales that are as yet unprocessed. This allows a
more representative value to exist for non-firm ATC at noon of the pre-schedule day when nonfirm ATC is offered. Non-firm ATC is offered by removing the firm transmission reserved
which is not scheduled during the Operating Horizon calculation by 2:30 p.m. each prescheduling day using implemented E-tags/schedules only. Non-firm ATC is reduced by nonfirm reservations (instead of non-firm schedules) to prevent having multiple unused non-firm
reservations exist for the same unused capacity.
6.1 Prior to Noon Day Ahead
Firm ATC is the remaining transfer capability available based on firm transmission
commitments.
Firm ATC = TTC – CBM – TRM –Existing Transmission Commitments (Firm)
Existing Transmission Commitments (Firm) include the following:
 Forecasted Native and Network Load attributable to a path in the Operating Horizon
Issued by: Cynthia B. Guillot, Director Transmission Policy & Contracts
Issued on: September 10, 2007
Effective on: September 11, 2007
Cleco Power LLC
FERC Electric Tariff, Third Revised Volume No. 1


Original Sheet No. 96D
Forecasted Generation for delivery to Native Load in the Operating Horizon
Firm Transmission Reservations in Operating Horizon for OATT and pre-Order 888
grandfathered contracts
Non-Firm Available Transfer Capability (Non-Firm ATC) is the remaining capacity available for
additional non-firm transmission reservations after the committed uses for firm reservations have
scheduled and existing non-firm reservations have been subtracted from TTC over a given time
horizon.
Non-Firm ATC = TTC – CBM – TRM – Existing Transmission Commitments (Firm) –
Existing Transmission Commitments (Non-Firm)
Existing Transmission Commitments (Firm) includes the following:
 Forecasted Native and Network Load attributable to a path in the Operating Horizon
 Forecasted Generation for delivery to Native Load in the Operating Horizon
 Firm Transmission Reservations in Operating Horizon for OATT and pre-Order 888
grandfathered contracts
Existing Transmission Commitments (Non-Firm) includes the following:
 Non-Firm Transmission Reservations in Operating Horizon
6.2 Pre-scheduled for Next Day
Firm Available Transfer Capability (Firm ATC) is not available after noon for next day during
operating horizon due to timing requirements in the OATT.
Non-Firm Available Transfer Capability (Non-Firm ATC) is the remaining capacity available for
additional non-firm transmission reservations after the committed uses for firm reservations have
been scheduled and existing non-firm reservations have been subtracted from TTC. Firm
transmission reservations are not used in the operating Horizon after noon in calculation of nonfirm ATC.
Non-Firm ATC = TTC – CBM – TRM – Existing Firm Transmission Commitments Scheduled
– Existing Transmission Commitments (Non-Firm)
Existing Firm Transmission Commitments Scheduled include:
 Energy schedules of firm reservations pre-scheduled for next day
Existing Transmission Commitments (Non-Firm) includes the following:
 Non-Firm Transmission Reservations in Operating Horizon
7.0 Calculations for the Planning Horizon
This period begins at the end of the Operating Horizon and extends through the end of the FERC
required posting period.
Issued by: Cynthia B. Guillot, Director Transmission Policy & Contracts
Issued on: September 10, 2007
Effective on: September 11, 2007
Cleco Power LLC
FERC Electric Tariff, Third Revised Volume No. 1
Original Sheet No. 96E
Firm Available Transfer Capability (Firm ATC) is the remaining transfer capability available
based on prior firm transmission commitments.
Firm ATC = TTC – CBM – TRM – Existing Transmission Commitments (Firm)
Existing Transmission Commitments (Firm) includes the following:
 Forecasted Native and Network Load attributable to a path in the Planning Horizon
 Forecasted Generation for delivery to Native Load in the Operating and Scheduling Horizons
 Confirmed Firm Transmission Reservations in all horizons including OATT and pre-Order
888 grandfathered firm commitments
Non-Firm Available Transfer Capability (Non-Firm ATC) is the remaining capacity available for
additional non-firm transmission reservations after the committed uses for firm reservations have
been subtracted from TTC. Existing non-firm transmission commitments are not included in the
base case power flow model.
Non-Firm ATC = TTC – CBM – TRM – Existing Transmission Commitments (Firm)
Existing Transmission Commitments (Firm) include the following:
 Forecasted Native and Network Load attributable to a path in the Planning Horizon
 Forecasted Generation for delivery to Native Load in the Operating and Scheduling Horizons
 Confirmed Firm Transmission Reservations in all horizons including OATT and pre-Order
888 grandfathered contracts
8.0 ATC Coordination
Cleco coordinates base case model development with interconnecting neighbors for reliability
assessments as well as calculation of ATC. In the calculation of ATC these models are the
starting point for determining the hourly, daily, weekly, and monthly ATC values.
Cleco participates in a weekly conference calls to discuss and schedule transmission outages
with neighboring transmission providers, which include, but are not limited to; Entergy,
Louisiana Energy and Power Authority, Lafayette Utilities System, and AEP-West. Planned
outages resulting from the conference call are one of the inputs into the ATC base models.
Concurrently, on a weekly basis, each participating transmission provider is to provide load
forecasts and basic generation dispatch for the scheduling and operating horizon by e-mail to
each participating transmission provider. Generation dispatch, load forecasts, and interchange, if
available, are all inputs for the ATC base case models to calculate ATC values.
9.0 Link to Actual ATC Algorithm
https://www.oatioasis.com/CLEC/CLECdocs/AttachmentC.pdf
Issued by: Cynthia B. Guillot, Director Transmission Policy & Contracts
Issued on: September 10, 2007
Effective on: September 11, 2007
Cleco Power LLC
FERC Electric Tariff, Third Revised Volume No. 1
Original Sheet No. 96F
ATC Process Flow Diagram:
START
Build Daily
or Weekly
Update
models?
Weekly
Gather Load
Forecasts,
Generation Dispatch,
Outage information,
and OATT & pre-888
transaction data
Daily
Insert Data
into
Coordinated
Base Case
Use Daily System
Assessment
Models
Calculate
FCITC values
for each path
Add TRM, and CBM values
to FCITC to obtain ATC &
is input into
TTC_Oasis_Automation.xls
spreadsheet
Add OATT & pre-888
Transactions to ATC
values to obtain TTC
values for each path
Save Hourly, Daily,
Weekly, Monthly TTC
and ATC Values in
Tracking.mdb for OASIS
Posting
Issued by: Cynthia B. Guillot, Director Transmission Policy & Contracts
Issued on: September 10, 2007
Effective on: September 11, 2007