Determination of transmission reliability margin using probabilistic load flow

According to NERC definition, Available Transfer Capability (ATC) is a measure of the transfer capability remaining in the physical transmission network for the future commercial activity. To calculate ATC, accurate and defensible TTC, CBM and TRM should be calculated in advance. This paper proposes a method to quantify time varying Transmission Reliability Margin (TRM) based on probabilistic load flow (PLF) using the method of moments. The uncertainties of power system and market, such as generation output, bus voltages, line outages, line flow and cancellation of power delivery contracts are considered as time varying complex random variables (CRV) in the PLF process. As a result of PLF analysis, Probability Density Function (PDF) of line flow and bus voltage at the transfer interface are acquired, and TRM with the desired probabilistic margin is calculated based on these PDFs. One distinguishing feature of the proposed method is that the TTC and TRM can be computed as a function of a specified probability margin. Suggested TRM quantification method is compared with the results with Monte-Carlo simulation and verified using 24 bus MRTS. The proposed method based on PLF shows efficiency and flexibility for the quantification of TRM.