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

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

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

4. 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

5. 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

6. 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

7. 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

8. 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)

9. 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)

10. 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

11. 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)

12. Questions