The project's location within the grid will dictate which losses are affected. Depending on whether the load is increased or decreased following a project implementation, the transmission and distribution line losses will either increase or decrease accordingly. A project located at the point of consumption will impact both these losses whereas a project located at the bulk generation level will impact neither. A project at the substation will impact the transmission but not the distribution losses.
Transformation of pre-project load data from data source location to project grid location:
The user may upload pre-project load profile data and indicate the data source location, that is, whether the data has been obtained from the generation, substation, or end-use level. If the user selects one of the reference AVERT profiles which consist of generation data, the data location will be automatically set to 'generation.' If the project grid location is different from the data source location, the pre-project load data is transformed to the project grid location before computing the project-related load changes. For example, if one of the reference AVERT pre-project load profiles are used for a Smart Charging project whose project grid location is end-use, the pre-project load data is first transformed from generation to end-use level by accounting for the transmission and distribution losses, before performing any project-relevant computations.
Transformation of post-project load data from project grid location to generation:
After a grid project has been implemented and the corresponding post-project load data generated, load data is transformed to the generation level before quantifying emissions. For example, in case of the same above-mentioned Smart-Charging project, after the project-relevant load changes have been computed at the end-use level, both the pre- and post-project load data is transformed to generation level by adding the transmission and distribution losses.
Calculation of Line Loss
The EIA estimates average total transmission and distribution (T&D) losses for the nation to be approximately 5%, and EPRI estimates that distribution systems have losses of around 3.64%. By combining these two figures, GridPIQ approximates that 27% of total losses are attributed to the transmission system, and 73% are attributed to the distribution system.
From the EIA FAQ:
"EIA has estimates for total annual losses related to electricity transmission and distribution (T&D) and other losses in the State Electricity Profiles. Data for each state and for the entire United States are in Table 10: Supply and Disposition of Electricity of each profile. To find the table, scroll down a Profile page to find the link under Table 1 for Full data tables 1-12. In the file, see the worksheet 10 Source-Disposition, and see the row for estimated losses in the table.
To calculate T&D losses as a percentage, divide estimated losses by the result of total disposition minus direct use. Direct use electricity is the electricity generated mainly at non-utility facilities and that is not put onto the electricity transmission and distribution grid, and therefore does not contribute to T&D losses."
GridPIQ uses the methodology described above to obtain state-level T&D (total) loss information for every available analysis year. To align regional granularity with other steps in the GridPIQ analysis, these state-level losses have then been aggregated to AVERT regions. For each AVERT data year, each state's total electric energy contribution to each eGRID subregion was determined using eGRID and EIA-923 data, and then the eGRID regions were aggregated to match the AVERT regions. These state-to-AVERT energy contributions were then computed as a percentage of total AVERT region generation for each year. The losses from each state were then weighted by the state's contribution to the net generation of the larger AVERT region and summed to determine a single loss factor for each AVERT region for each year.