Transmission Planning Base Case Loads & Transmission System Model Jameson Thornton Anupama Pandey Marco Rios 03/31/2014

Base Case Load Overview Objectives 1 Method 2 Process 3 This is another option for an Overview slide.

Objectives (requirements) CAISO 1in5 system load suitable for high voltage system (230-500 kV) assessment 1in10 area load suitable for local area network (60-230 kV) assessment WECC Seasonal peak/partial peak/off peak loads as specified

Base Case Load Method Base Case Load Determine “ appropriate ” PG&E division load CEC system forecast Temperature, coincidence, Seasonal factors Distribution planning forecast Muni load Conforming load Non conforming Other load, e.g., station service EMS data Base Case Load Loss and other adjustments

Seven Areas (20 Divisions) Preliminary Draft Preliminary Draft Seven Areas (20 Divisions) North Valley Humboldt North Coast North Coast & North Bay Central Valley Sacramento, Sierra, Stockton & Stanislaus San Joaquin Valley Yosemite, Fresno & Kern Central. Coast & Los Padres Greater Bay Area SF, Peninsula, De Anza, SJ, East Bay, Diablo & Mission

Preliminary Draft Preliminary Draft Process From system level forecast derive the area and the division level forecast PG&E system is divided in to 7 areas Areas are further divided into 20 divisions Each division may have several distribution planning areas Derive Load Vs. Temperature relationship for each division Develop the starting point for the load for each division Meld Distribution and Muni forecast into Division forecast Allocate Division Loads to Transmission Buses

Load Growth Load growth is based upon: Two step process: PG&E distribution load forecast CEC load forecast Two step process: Step 1: PG&E load growth (from CEC forecast) for the year is determined Step 2: Total PG&E load growth allocated to the division, based on the relative magnitude of the load growths projected for the divisions by the distribution planners Adjusted for temperature requirement

PG&E’s Transmission System PG&E’s transmission system encompasses a large and diverse geographical area that includes vast networked systems (vs. radial) Provides service to over 15 million people 70,000 square miles Over 18,000 circuit miles of transmission lines PG&E’s transmission system is divided into 7 local transmission areas Natural geographical boundaries Electric system interaction Weather pattern The seven transmission planning areas are further divided into 20 sub-areas (Divisions)

PG&E Transmission System Model PG&E is registered with NERC as a Transmission Owner CAISO is the Planning Authority for the PG&E system & PG&E follows the CAISO Transmission planning process, procedures and standards CAISO span of control of PG&E system is from 500KV to 60 KV PG&E must demonstrate that its transmission system complies with all applicable NERC/WECC/CAISO reliability planning standards. Maintenance of transmission system models NERC/WECC requires its members to provide detailed and accurate transmission system representation Conduct transmission system assessment (other studies not related to NERC Compliance are also performed) PG&E defines transmission voltage as 60 kV and above and as such the associated systems are modeled in power flow base cases for transmission planning studies (Distribution voltage class includes 21 kV and below - not modeled)

PG&E Transmission System Model PG&E’s transmission system model includes detailed representation of all: Transmission lines (sometimes in several segments) Power transformers Generators Shunt devices (SVC, MSC, SVD, etc.) Loads (conforming, non-conforming, self-generation and generation-plant loads) Note: Some substations connected only at the distribution level are not explicitly modeled in the transmission system power flow model. Their load is aggregated at the source substation with transmission level service. WECC is moving towards a detailed load model for use in dynamic stability simulations PG&E’s current load modeling assumption provides a good foundation for developing detailed load models for future use

PG&E Transmission System Model Loads are aggregated at the high side of the distribution transformer (transmission level) This approach results in a transmission system model with approximately 1300 buses with load (including other utilities such as SMUD)

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