A sequence networks-based methodology for investigating voltage unbalance in distribution networks with renewable generation is presented. The sequence networks are derived from the original asymmetrical three-phase network, and then interconnected to study sequence voltages and unbalance propagation through the network. The approach enables to analyse the influence of line impedance, load demand and network topology on voltage unbalance caused by distributed generation in the network. The critical factors which impact the unbalance severity and the propagation mode are also identified. The approach is validated by comparing calculated sequence voltages with the results obtained by phase voltage-based methodology.