The aluminum bridges studied were instrumented and subjected to a range of pedestrian-load tests to understand the performance of existing periodic models in predicting the dynamic response. The performance of these models (assuming pedestrian forces to be a summation of harmonics) has thus far only been. 15 Feb This paper addresses the issue of power system load modelling. In power system and voltage stability studies, only aggregate loads at high voltage buses are needed. Due to difficulties in determining appropriate load models at high voltage buses, the classical exponential static load model is still often. NREL's load modeling work is focused on the development and improvement of distributed energy resource models from distribution and bulk system perspectives.