NERC ATC Standards

1. NERC ATC Standards MOD-004, -008, -001, -028, -029, -030

2. Apply to all “ATC Paths” which are defined as “Any combination of Point of Receipt and Point of Delivery for which ATC is calculated; and any Posted Path.” • Cover calculation of TTC, ATC, TRM & CBM • New standard becomes effective one year after approval by FERC • Impact of the new standard may be profound

3. MOD-004 CBM Standard • Applies only to those Transmission Service Providers that “have elected to maintain CBM” • Can only be called upon by those who maintain it “when experiencing a declared NERC Energy Emergency Alert (EEA) 2 or higher. (MOD-004 R10) • Documentation required in the form of a CBMID (CBM Implementation Document) • Very few entities in the WECC maintain CBM

4. MOD-008TRM Standard • Applies only to Transmission Operators that “maintain TRM” • Documentation required in the form of a TRMID (TRM Implementation Document) • Ok to use TRM to accommodate uncertainty associated with- • Load Forecast -Load Distribution • Topology -Loop flow impacts • Simultaneous Path action -Generation dispatch • Sys Operator response -Reserve Sharing req • Inertial response and frequency bias

5. MOD-001Available Transmission Sys Capability • Each TO shall select one of the 3 recognized methodologies for each ATC path per time period • Documentation required in the form of a ATCID (ATC Implementation Document) • Within 30 days of receiving a request must provide certain technical data such as load forecasts, unit commitments and order of dispatch, power flow models etc (R9.)

6. Three ATC calculation methodologies recognized by the standards: • Area Interchange Methodology (MOD-028) • Used by FPL, Southern Company & others • Rated System Path Methodology (MOD-029) • Used by most utilities in the WECC • Flowgate Methodology (MOD-030) • Used by PJM, MISO, SPP, TVA, Entergy, Duke, BPA, CAISO & others

7. MOD-029 will require that the TTC or path rating be established via a “WECC-like” path rating process • Power flow studies must demonstrate flowability for n-0 and n-1 (MOD-029 R2.1) • Same methodology applies to both prevailing and non-prevailing directions of flow (MOD-029 R2.2) • Simultaneous interaction must be checked and mitigated if encountered (MOD-029 R2.5) • Existing ratings grandfathered only if established before Jan 1, 1994 and not changed since then (MOD-029 R2.7) • Separate report for each “ATC Path” must address each requirement in the standard (MOD-029 R2.8)

8. Impact on Manpower • To conduct the required power flow studies to recalculate TTC (path ratings) • To provide technical data to others if required • To provide increased documentation (TTC reports, ATCID, TRMID, CBMID etc)

9. Impact on TTC • If path rating wasn’t established via rigorous power flow analysis TTC will likely be reduced due to • Difficulty proving flowability • Simultaneous interaction with neighboring paths • Reduced TTC may result in paths that are oversubscribed causing • Default on contractual obligations • Uneconomic re-dispatch of resources

10. QUESTIONS NEEDING TO BE ADDRESSED • Are all the paths you have posted on OASIS “Accepted Rating” paths? • If not, have you determined what manpower will be required to recalculate the TTC for those that aren’t? • Do you expect any of your path ratings to go down when recalculated? • How do we deal with paths that become oversubscribed due to reduced TTC? • How do we deal with simultaneous interactions with neighboring paths that were not identified until ratings were recalculated?