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 regional 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 regional 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-related computations.
Transformation of post-project load data from project grid location to data source location
After a grid project has been implemented and the corresponding post-project load data generated, load data is transformed to the data source location (‘generation’ set by default) before quantifying impacts. For example, in case of the aforementioned Smart-Charging project, after the project-related 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.
Note that the emission impact is a special case in that emissions are always quantified at the ‘generation’ level. Therefore, both pre and post-project load are converted to the ‘generation’ level from the grid location for emissions impacts.
Calculation of Line Loss
The U.S. Energy Information Administration (EIA) estimates average total transmission and distribution (T&D) losses for the nation to be approximately 5% of the total electricity transferred in T&D annually (averaged from 2013 to 2017). 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 national-level T&D (total) loss information for every available analysis year. This national average is used for all reference regional profiles as well as user uploaded pre-project load data.