September 2, 2010 DCS Event

Reliability Committee November 17, 2010Peter Brandien

Highlights

• New England was experiencing a late season heat wave

• September 2nd peak load of 26,098 MW was an all-time September peak

• System Operator reserve monitor indicated surplus in both 10 and 30 minute operating reserves

• Experienced the source loss that was setting the 10-minute operating reserve requirement

• Both on-line and off-line resources under performed

• Failed to recover from the source loss within the NERC Reliability Standard requirement of 15 minutes

NERC Reliability Standard Requirement

• Standard BAL-002 - Disturbance Control Performance– R4. A Balancing Authority or Reserve Sharing Group shall meet

the Disturbance Recovery Criterion within the Disturbance Recovery Period for 100% of Reportable Disturbances. The Disturbance Recovery Criterion is:

• R4.1. A Balancing Authority shall return its ACE to zero if its ACE just prior to the Reportable Disturbance was positive or equal to zero. For negative initial ACE values just prior to the Disturbance, the Balancing Authority shall return ACE to its pre-Disturbance value.

• R4.2. The default Disturbance Recovery Period is 15 minutes after the start of a Reportable Disturbance. This period may be adjusted to better suit the needs of an Interconnection based on analysis approved by the NERC Operating Committee.

– Reportable Disturbance is defined as any contingency ≥ 80% of the First Contingency Loss

Event Overview – Initial Conditions

System Conditions at the time of the contingency:

Reserve Component Required Actual Surplus

Ten Minute Reserves 1390 1784 394

Spinning Reserves 696 988 292

Operating Reserves 2075 2862 787

Forecasted* Actual Difference

System Load (HE14) 24861 25173 312

* Interpolated value for 13:09 from the hourly forecast, assuming hourly load is forecasted at midpoint of each hour.

Event Overview

• At 13:09 New England experienced a source loss of approximately 1400 MW

• NPCC Shared Activation of Reserve was limited due to heavy imports from New York

• Operating Reserves dispersed across many units due to the size of the first source contingency and the operating response rates of available resources

• Recovery of ACE to pre-contingent value took approximately 23 minutes

Timeline

Time Event ACE

13:09 Begin Event -59

13:11

Contingency Dispatch Approved and Delivered-146 Generators sent DDPs to move up; +1925 MW

-56 Startups; +935 MW-90 Online; +990 MW -1588

13:14 Began receiving NB SAR (50 MW) -1286

13:23

Non-Contingency Dispatch Sent after operators determined that the response to the contingency dispatch was insufficient to recover -223

13:24 DCS STANDARD VIOLATED (15 minutes) -212

13:32 ACE Returned to pre-contingent value -29

13:33 ACE Returned to Zero 7

Recovery Actions

• Desired Dispatch Points (DDP) were sent to 146 Generators via Electronic Dispatch to increase output for a total of 1925 MW

• 56 start ups for a total of 935 MW

• 90 online units for a total of 990 MW

• At ~13:23, an economic (non-emergency) DDP was sent in response to the Contingency Dispatch not being sufficient to recover the ACE within 15 minutes

• ACE was restored to its pre-contingent value at ~13:33

Interconnection Frequency

ACE Recovery

Transmission System Performance

• The Eastern Interconnection inertial response increased NY-NE interface flow by approximately 90% of the source loss

• NY-NE flows were initially at the N-1 transfer limit

– Flows increased from ~1,400 MW to over 2,600 MW

– N-0 limit was approximately 2,900 MW

• Limit violations are required to be cleared within 30 minutes (NERC Standard: TOP-007)

– NY-NE Interface flows reduced to N-1 limit in 21 minutes

Interface Transfer Recovery

Generator Response

• Summary of generator response

– Of the 56 start ups:

• 936 MW dispatched

• 673 MW produced

• 263 MW deficiency

– Of the 90 online units:

• 986 MW dispatched

• 398 MW produced

• 588 MW deficiency

Immediate Actions

• ISO New England self-reported violation of BAL-002 Requirement 4.1 the afternoon of September 2

• Ten Minute Reserve requirement raised to 110% of the largest single source contingency

• Ten Minute Spinning Reserve requirement raised to 50% of the new requirement (55% of largest contingency)

• Maintain a mix of SAR + Ten Minute Reserves of at least 140% of largest single source contingency

Additional Requirements

• After the end of each quarter a Balancing Authority’s performance is evaluated by the Regional Entity (NPCC) and NERC

– Based on the September 2nd event, effective November 1st ISO New England’s 10-minute reserve requirement was increased to 112.7% of the largest first contingency (NERC Reliability Standard BAL-002)

– Performance for the 4th quarter of 2010 will be evaluated in January 2011 for ability to return to 100% effective February 1st

ISO New England’s Internal Analysis• Evaluated Operator Tools and Surveyed Designated

Entities to gain a better understanding of NERC violation• Findings:

– Need improvements to procedures or standards for:• Generator displays and alarms• Acknowledgement and compliance of DDPs sent to generators by ISO • Testing and verification of the functionality of communication

equipment for receiving and responding to DDPs• Generator performance audits• Generator training

– Need improvements to ISO systems related to:• Real-Time calculation of Operating Reserves• Real-Time modeling of generators’ response• Ability to monitor DDP receipt & acknowledgement by generators

Conclusion

• ISO participating with NPCC on Event Analysis, and expects to brief NPCC on its causal analysis in December

• ISO expects to bring various Operating Procedure and other Rule changes to NEPOOL Committees in 2011