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March 2003 Operations Summary

Bill BlevinsManager Operations Engineering

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• March 2008– Wind Capacity ~ 5,000 MW– Load 22,700,794 MWH– #Outage Gen 419– #Outage Trans 2216

• March 2009– Wind Capacity ~ 8,000 MW– Load 22,150,823 MWH– # Gen Outage 466– # Trans Outage 2575

March 08 to March 09 Comparison

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Comparison 2008-2009

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Top March Congestion items

ERCOT Stability IROLs

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NERC Criteria

• FAC-11– R3.3. A process for determining which of the stability limits

associated with the list of multiple contingencies (provided by the Planning Authority in accordance with FAC-014 Requirement 6) are applicable for use in the operating horizon given the actual or expected system conditions.

• FAC-14– R6. The Planning Authority shall identify the subset of multiple

contingencies (if any), from Reliability Standard TPL-003 which result in stability limits.

• R6.1. The Planning Authority shall provide this list of multiple contingencies and the associated stability limits to the Reliability Coordinators that monitor the facilities associated with these contingencies and limits.

• R6.2. If the Planning Authority does not identify any stability-related multiple contingencies, the Planning Authority shall so notify the Reliability Coordinator.

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TPL-003 Multiple Contingency Criteria

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TPL-003 Multiple Contingency Criteria continued

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Standard TOP-007-0 — Reporting SOL and IROL Violations

• R2. Following a Contingency or other event that results in an IROL violation, the Transmission Operator shall return its transmission system to within IROL as soon as possible, but not longer than 30 minutes.

• R3. A Transmission Operator shall take all appropriate actions up to and including shedding firm load, or directing the shedding of firm load, in order to comply with Requirement R2.

• R4. The Reliability Coordinator shall evaluate actions taken to address an IROL or SOL violation and, if the actions taken are not appropriate or sufficient, direct actions required to return the

• system to within limits.

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Market tool for Zonal Balancing Deployments

Current Time 2145

MARKET Flow Time 22:00

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Voltage Stability Limit in ERCOT identified as an IROL

The interface for the North to Houston includes the four 345 KV lines

Jewett to TH WhartonJewett to TomballGibbons Creek to O’BrienRoans Prairie to Kuykendahl

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West to North Dynamic Stability

• Six 345kv transmission lines are measured and defined as the West North Dynamic Stability limit interface.

• These six 345kv transmission lines are:– Mesquite to Graham (measured as entering Graham)– Sweetwater to Graham (measured as entering Graham)– Morgan Creek to Graham (measured as entering Graham)– Bowman to Graham (measured as leaving Bowman) – Bowman to Jacksboro SS (measured as leaving Bowman)– Red Creek to Comanche (measured as entering Comanche SS)

ERCOT Information Available to Particpants•North to Houston Voltage

•West to North Dynamic Stability

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Day Ahead

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Voltage Stability

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Messages Operations Post Real-Time

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CSC Calculator Results

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Real-Time Flows

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VSAT Results

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Info Operations Post After the fact

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March 29 information