This paper presents an object-oriented modeling software, LoadLab, for
the load analysis of electricity distribution networks. A characteris
tic feature of LoadLab is that it uses load pattern models where consu
mption is represented as the sum of the daily and weekly rhythms of co
nsumption, the effects of outdoor temperature on consumption, and rand
om variation. With object-oriented modeling methods we can manage the
hierarchical structure of the distribution network which is reflected
in the load models. Network load patterns and their confidence interva
ls are obtained by combining existing load pattern models and consumer
characteristic data.