Residential load models for network planning purposes

Network planning is a major task for every electric utility and the major goal is to comply with the loading capacity of the equipment and to provide the desired voltage to the customer. The difficulty is to model the customers demand and the loading of the equipment. A worst-case scenario coupled with an estimation of the load increase for the planning horizon is a typical engineering approach for the dimensioning of the network. Especially for low-voltage network planning little is known about the residential loads. One characteristic of these loads is the diversity and stochastic. The networks do not have to withstand the worst possible combination of demands. The effect of diversity changes with the number of customers and evens out. The coincidence factor takes account for this behavior calculating the demand of several customers. In this paper the characteristics of residential loads are shown and several options for the determination of the maximum load are explained and compared. This includes the coincidence factor, Velander's formula, the Herman-Beta method and the bottom-up approach.