Assessment of errors introduced by common assumptions made in power system studies

Power system studies using commercial or in-house developed software are performed making several assumptions. This paper analyzes the errors introduced by the most common modeling simplifications made for load-flow, short-circuit, and transient stability studies. Load-flow studies for transmission systems almost invariably rely on the positive-sequence approach. While this may be acceptable for most transmission system conditions, errors of up to 15% can be found by not considering the unbalanced nature of power systems components. Errors larger than 10% are found in short-circuit studies by using symmetrical components. Common assumptions also introduce differences in transient stability analysis. The results for the studied test case show differences of up to 14% in the determination of the maximum clearing time. With the current development status of computing hardware and available algorithms, more accurate modeling is currently available even for large systems.