1Texas Nodal Texas Nodal CRR Annual Model Discussion DRAFT By John Moseley, ERCOT

2Texas Nodal Current Information As detailed in the Nodal Protocols, the cases for the CRR Annual Auction will be constructed up to 18 months before the period in which the CRR is valid Modeling network topology information 18 months in advance has been historically limited to information provided by the TSP planning departments TSP Planning departments traditionally have used bus-branch models to conduct their studies As a comparison, TSP Operations departments traditionally have used a node (breaker) model to monitor the electric grid You might be asking: Why is this important?

3Texas Nodal Example: Modeling Differences of the same station Operations Model Representation “breaker” Model Planning Model Representation “bus-branch Model”

4Texas Nodal NMMS conversion to PSS/E: CIM to PSS/E Transformation

5Texas Nodal Addressing Issues Issue 1: –IEC CIM 11 CPSM standard which is what NMMS is using as its baseline is used to model the Operations Breaker Model. No account for Planning Models –Planned changes to the bus-branch model more than likely do NOT exist in the operations format 18 months out. –Due to construction uncertainty (details of breaker configuration), many TSP Operations dept can not convert the bus-branch planning model to a Operations Breaker Model until <6months from installation date. Issue 2: –There currently is no CIM standards for the a bus-branch Planning Model –Planning CIM working group starting in 4Q2006 and planned to complete by end of 2007 Issue 3: – CRR Auction Engine tool uses a planning (bus-branch) Model

6Texas Nodal Visual Timeline Annual CasesMonthly Cases

7Texas Nodal Current Interpretation CRR Requirements The CRR Network Model input into the CRR System shall be a CIM compliant file converted to PSS/E RAWD format file following the requirements noted below. The same CIM compliant file will be posted as the CRR Network Model. Although not required, the expectation is to also post PSS/E RAWD format file. –CRR requirement can be satisfied for CRR Monthly auctions but can not be satisfied with the annual auctions. –Need to determine TPTF position on annual CRR auction topology posting Optional Plan ERCOT will post only PSSE formatted RAWD files for the CRR annual Auction until Planning CIM becomes available. After which, when planning CIM becomes available, both formats will be posted for the CRR annual Auction.

8Texas Nodal CRR Model Discussion Questions?

9Texas Nodal Network Model Format (PSS/E vs. CIM) Why PSS/E? –Format is de-facto industry standard –Bus/branch model –CRR Requires a bus/branch model –CRR COTS imports PSS/E natively (out-of-box) –Network Model size using PSS/E format is significantly smaller than the same model in CIM XML CIM Characteristics –Well accepted Industry standard –CIM model extensions may be required to cover CRR needs –From the network model perspective, CIM describes bus/breaker model that is much more detailed –NMMS is CIM compliant – can export in both CIM and PSS/E –CIM -> PSS/E possible (out-of-box feature of the NMMS tool); PSS/E -> CIM not possible –For CRR CIM bus/breaker must be translated to bus/branch by either: Sender/Provider (NMMS – Low Cost, Low Risk, No Schedule Impact) Receiver/Consumer (CRR - High Cost, High Risk, High Schedule Impact) Integration Layer (High Cost, High Risk, High Schedule Impact) The proposed approach –NMMS publishes CIM and PSS/E –CRR uses PSS/E –Minimize cost and risk Leverages the best of both Worlds –CIM compliant at the network model source (NMMS) –Leverages PSS/E as de-facto standard native to the CRR off- the-shelve product –Consistent with Nodal Program approach to support applications’ native interfaces and have integration layer or data provider being responsible for data transformations.