Methodology

50% Area Load Methodology Using Corrected Loss Matrix

In the 50% Area Load Methodology Using Corrected Loss Matrix, the loss factors are determined directly from the coefficients of a system loss matrix which is derived from the system topology.  The system loss matrix ‘R’ is also known as the real component of Z-bus Matrix.  Each individual term of the loss matrix ‘R’ is corrected and the corrections are based on bus voltages, bus angles, and generator and load power factors obtained from the base-case load flow solutions.

In the ‘area load’ method, the generator for which the loss factor is being determined is designated as the swing generator, and load is changed at every bus in the area by a constant ratio.  For this calculation the area is selected to be the entire Alberta system.  Again loss factor is calculated equal to the change in losses for the resultant change in generation at the swing bus.

It can be shown mathematically that the losses assigned by the area load adjustment methodology are twice the actual losses. The loss factors calculated using area load adjustment is reduced by 50% to determine the average losses and unassigned losses and the shift factor will be recalculated. One single transmission raw loss factor number is determined which is derived from the average of the 12 seasonal scenarios.

Each year, the total system losses (energy) are estimated prospectively using the most current information available.  The corresponding losses that would result from the application of the raw loss factors are also determined.  An algorithm is used to shift all raw loss factors up or down until the two total loss volumes match.  The amount of shift necessary becomes the annual 'shift factor’.  The new adjusted raw loss factors are called normalized loss factors.

According to Alberta Transmission Regulation the normalized loss factors should not exceed +12% or -12%.  A linear compression algorithm with clipping is used to bring all loss factors within the given bandwidth. Compression will not be required if all normalized loss factors are within the limits as prescribed.

The links below provide a detailed description of all four parts of the methodology.  For more information on loss factors methodology, please contact the AESO at lossfactor@aeso.ca.