Marginal Distribution System (and Transmission System) Losses Regional Technical Forum August 5, 2008
Background • ProCost currently assumes: • At the April 29th RTF meeting, Jim Lazar proposed the use of a “marginal” distribution system loss ratio, which is higher than the normal distribution system loss ratio.
Review of the Original Proposal Percent Losses are proportional to the square of the load.
A Minor Adjustment Losses are proportional to the square of the load.
Are Marginal Losses are Higher than Total Losses? • Losses=I2R • Marginal Losses=dLosses=2IRdI (derivative) • Assuming line losses are caused entirely by I2R losses, voltage is held constant, and resistance is constant, “marginal losses as a percent of energy savings” is two times “total losses as a percent of total energy”. • See “proof” for more details:
However… • Is voltage really held constant? • If so, what does it take ($ or energy or both) to hold it constant?
How To Incorporate into ProCost • Since marginal distribution system losses vary with both the system load shape and the measure savings shape, each measure’s load shape has a unique marginal distribution system loss ratio (marginal dist. system losses to energy savings).
ProCost (Continued) • However, we know line losses are not caused entirely by I2R losses. • This graph shows line losses at various mixes of I2R losses and “other losses” (assumption: marginal “other losses” do not vary with the load)
Decisions • Accept this analysis and program ProCost to generate measure-specific shaped “marginal distribution system loss ratios” to calculate busbar savings? • Components of Distribution System Losses (What Percent of the total losses are due to I2R losses?) • Applicability to Marginal Transmission System Losses • Seek further input?