Transmission/Distribution Loss Allocation

Power flow, when annotated on to a power network one-line diagram, as shown in the following figure, could be viewed as a directed graph.

Transmission/distribution loss could be allocated along the transmission path to the load points or generation source points. Theory and algorithm for the allocation have been discussed in great detail in the book by Prof Wang (Ref[1]).

Loss Proration

Power transmission/distribution loss are prorated at each bus, along the power flow path, proportional to the value of active power in and out of the bus, including load and generation on the bus. The following two simple samples are used to illustrate the idea. For simplicity, here we assume loss is always 5% of the branch power flow. Therefore 100(5) in the diagram means 100MW branch power flow with 5MW loss. In actually situation, the loss is calculated using the loadflow results.

In Fig-A, 100MW is supplied to Bus-B with 5MW loss. On Bus-B there are two loads (L1, L2). The transmission loss (5MW) will be prorated to the loads according to the amount of power usage. Therefore L1, which uses 60MW, will be allocated 3MW, and L2 2MW.

In Fig-B, 100MW is supplied to Bus-B with 5MW loss. The power is then transmitted to Bus-C and Bus-D. Using the same prorate concept, Bus-C should be allocated (3MW + 3MW) transmission loss, and Bus-D (2MW + 2MW) loss.

Although only simple radial network situations are discussed here, the concept could be applied to practically any power network, radial or looped, as long as the network does not have closed active power loop, which only could be existed in loss-less super-conductive situation. This has been proved in theory in Prof Wang's book (Ref[1]).

Loss Allocation

After a coverged lodflow calculation, system total loss could be allocated to all load points or all source points. The following are loss allocation results using the loss proration approach for the IEEE 14-Bus test case (Input data file, ODM xml file, Loadflow results).

To Load End Points

The following are load point loss allocation results for the IEEE 14-Bus test system.

Load Loss Allocation

Total Loss = 13.43 MW

BusID LossAllocFactor Allocated Loss(MW)

------------------------------------------------------------------------

0002 0.037 0.49

0003 0.414 5.56

0004 0.183 2.46

0005 0.023 0.31

0006 0.034 0.45

0009 0.113 1.52

0010 0.036 0.48

0011 0.013 0.17

0012 0.023 0.31

0013 0.053 0.72

0014 0.071 0.96

To Source Points

The following are source point loss allocation results for the IEEE 14-Bus test system.

Gen Loss Allocation

Total Loss = 13.43 MW

BusID LossAllocFactor Allocated Loss(MW)

------------------------------------------------------------------------

0001 0.914 12.28

0002 0.086 1.15

Use InterPSS Loss Allocation

The Loss Allocation algorithm is currently available in InterPSS Cloud Edition. To use it follow the steps below:

Go InterPSS Cloud Edition
Upload a loadflow file. Please select appropriate loadflow file format
Click the Upload button to submit your loadflow case
Click the Loss Allocation link to run InterPSS Loadflow and Loss Allocation.

Reference

[1]王锡凡, "现代电力系统分析" (Modern Power System Analysis), 科学出版社 2003