ERCOT Wholesale Market SubcommitteeJanuary 12, ERCOT Wholesale Market SubcommitteeJanuary 12, ERCOT/IMM/PUCT Proposal for Redaction of State Estimator Data Wholesale Market Subcommittee January 12, 2011

ERCOT Wholesale Market SubcommitteeJanuary 12, ERCOT Wholesale Market SubcommitteeJanuary 12, Original Nodal Protocol Language (Nov. 2009) ….. (4)Every hour, ERCOT shall post on the MIS Secure Area the following information: ….. (b) Transmission flows and voltages from the State Estimator; ….. (d) Transformer flows, voltages and tap position from the State Estimator; ….. The original Protocol language in Section , Data Inputs and Outputs for the Real-Time Sequence and SCED, generated stakeholder discussion over the items in red below. Disclosing all of this information in Real-Time could threaten the confidentiality of resource-specific outputs and bids/offers. Nodal Protocol Revision Request (NPRR) 209 and Project No were initiated to resolve confidentiality concerns in both the PUC Substantive Rules and ERCOT Protocols.

ERCOT Wholesale Market SubcommitteeJanuary 12, ERCOT Wholesale Market SubcommitteeJanuary 12, Project No – Commission’s Order Adopting Amendment to § As Approved at the October 22, 2010 Open Meeting Highlights of the new PUC Substantive Rule changes impacting State Estimator (SE) data include the following: (E)After the start of operation of the market under a nodal market design, ERCOT shall begin posting transmission flows, voltages, transformer flows, voltages and tap positions (i.e., State Estimator data) 60 days after the day for which the data were accumulated or other time interval as established in clause (ii) of this subparagraph. The data released shall be made available simultaneously to all market participants... (ii) … ERCOT shall, by the start of the nodal market, develop and post a redacted version of State Estimator data, as soon as reasonably practicable after collection of the data, so long as a redacted version excludes information (including but not limited to, voltages, transmission flows and transformer flows) from which resource-specific output levels or offer curves could continually and systematically be derived. Concurrently, in conjunction with the Independent Market Monitor and the commission Staff, ERCOT, through its stakeholder process, shall develop protocols that detail, at a minimum, the methodology, duration and posting requirement of a redacted version of the State Estimator data. The redacted report methodology developed through the stakeholder process shall be completed within 90 days of the start of the nodal market. Continues on next slide….

ERCOT Wholesale Market SubcommitteeJanuary 12, ERCOT Wholesale Market SubcommitteeJanuary 12, Project No (cont.)... If ERCOT is unable to develop a cost effective protocol for the redaction process of the State Estimator data within 90 days of the start of the nodal market, then the following information shall be released as soon as reasonably practicable: (I)Current commercially significant constraints (CSCs) and closely related elements (CREs) line flows that are embodied in the competitive constraint list from the Competitive Constraint Test; (II)For phase shifting transformers, tap positions and line flows; (III)Voltages at all buses; (IV)Line flows on lines that make up interfaces (import, export, flow gate, or stability); and (V)Line flows on DC ties. Regarding “backstop” data, ERCOT is currently posting items (I), (II), most of (IV) and (V) above. By March 1, 2011, ERCOT will post item (III) above to comply with the Rule. On November 16, 2010, the ERCOT Board of Directors approved NPRR209 incorporating the Commission’s changes in the PUC Substantive Rules into the EROCT Protocols. “backstop”

ERCOT Wholesale Market SubcommitteeJanuary 12, ERCOT Wholesale Market SubcommitteeJanuary 12, The Continuum of SE Data Real-Time Data: 38 lines, 7 transformers (phase shifters) (Op Day + 60) Data: *everything* 5,643 lines, 1,511 transformers RedactDisclose “Compromise Region” Max security Min information Max information Min security

ERCOT Wholesale Market SubcommitteeJanuary 12, ERCOT Wholesale Market SubcommitteeJanuary 12, ERCOT Proposed Redaction Methodology GT1T2T3 LineIDFromStToStToMWToMVARFromMWFromMVAR AGT1xxx BT1T2xxx CT2T3xxx A B C Redaction is based on lines’ proximity to stations containing resources. Lines are redacted based on their “electrical distance” from generating stations. Gen ties + 1 station: Redact gen ties plus all lines at next stations Gen ties + 2 stations: Redact gen ties, plus all lines at next two stations Gen ties only: Redact only gen ties (all lines incident at gen stations)

ERCOT Wholesale Market SubcommitteeJanuary 12, ERCOT Wholesale Market SubcommitteeJanuary 12, Breakdown of Methodology Results # Lines Excluded # Stations Excluded# Lines Included Redaction Method 345KV138KV69KVTotal Gen Lines Only Gen Lines + Next Station Gen Lines + 2 Stations Gen Lines + 3 Stations Gen Lines + 4 Stations Gen Lines + 5 Stations Gen Lines + 6 Stations *Total lines in ERCOT: 5,643

ERCOT Wholesale Market SubcommitteeJanuary 12, ERCOT Wholesale Market SubcommitteeJanuary 12, Redact Gen Ties + 6 stations

ERCOT Wholesale Market SubcommitteeJanuary 12, ERCOT Wholesale Market SubcommitteeJanuary 12, Redact Gen Ties + 5 stations

ERCOT Wholesale Market SubcommitteeJanuary 12, ERCOT Wholesale Market SubcommitteeJanuary 12, Redact Gen Ties + 4 stations

ERCOT Wholesale Market SubcommitteeJanuary 12, ERCOT Wholesale Market SubcommitteeJanuary 12, Redact Gen Ties + 3 stations

ERCOT Wholesale Market SubcommitteeJanuary 12, ERCOT Wholesale Market SubcommitteeJanuary 12, Failure of 3-station method at WHTTAIL

ERCOT Wholesale Market SubcommitteeJanuary 12, ERCOT Wholesale Market SubcommitteeJanuary 12, WHTTAIL looks OK w/ 4-station

ERCOT Wholesale Market SubcommitteeJanuary 12, ERCOT Wholesale Market SubcommitteeJanuary 12, Conclusion In order to comply with the Commission’s Order in Project No and PUC Subst. R (E)(ii), ERCOT will sponsor a Nodal Protocol Revision Request (NPRR) in the near future that formalizes the proposed methodology, duration and posting requirement of a redacted version of the State Estimator data. – Methodology: ERCOT recommends using the proposed methodology to exclude all transmission lines up to a point where resource-specific output levels or offers could not continually and systematically be derived. – Duration: ERCOT recommends that the redacted version of SE data be posted no sooner than 24 hours after the Operating Day. – Posting Requirement: ERCOT recommends that the redacted version of SE data be posted on the MIS Secure Area. Questions?