Discussion: Use of RAPs in system operations

Kris Dixit

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Goals of this presentation• Better understand how RAPs are utilized by ERCOT system operations to

manage grid reliability• Discuss potential issues with divergence between the CRR markets and

the DA/RT markets• Discuss impacts to economic and reliability transmission planning

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RAPs (Remedial Action Plans)• Steps that ERCOT can take to reduce loading on a post contingency

overloaded element in the event the contingency occurs• Allows ERCOT to deactivate constraints that are protected by RAPs since

there is no real reliability issue• RAPs are generally defined as contingency constraint pairs. For example:

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How ERCOT utilizes RAPs• ERCOT operations looks at RAPs as applying to a contingency rather than

a contingency constraint pair• Accordingly if there is a different constraint for a given contingency, they

apply the RAP even though the RAP was not initially designed for that constraint.– Ex: The DALNRYS5 RAP has been used to manage other constraints not listed in the RAP

definition

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Issues• If we take the DALNRYS5 contingency, the outage of the Apollo auto is the

action during the post contingency overload of the Apollo to Richardson East 138kV line.

• Depending on the direction of the flow on Apollo Auto, for that contingency the Apollo Auto has a meaningful LODF % on more than 100 lines.

• Planning Inconsistencies:– It is our understanding that ERCOT in its economic and reliability transmission planning

uses contingency constraint pairs in accounting for RAPs.– If RAPs are being used as part of the contingency definition, should all possible

combinations be considered when the RAPs are being used for transmission planning?– Should rate-payers be charged for planned transmission lines that resolve overloads

that do not exist in real-time?

• CRR inconsistencies: – Should all possible combinations of RAP-constraint pairs be considered when running

the CRR engine?– For example the Contingency constraint pair as part of DALNRYS5 RAP (Apollo to

Richardson East 138kV line) was allowed to bind in the August 2012 CRR auction and generated a shadow price of $14,806/MWH for 186MWs.

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In Conclusion• We believe that ERCOT operations should have all the tools it needs to

reliably manage the ERCOT grid.• Expanding the use of RAPs to manage constraints other than the one in

the original definition seems to be a reasonable utilization of existing tools• However, we need to reconsider how RAP-constraint pairs are considered

in transmission planning and the CRR engine to maintain consistency

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