Residential solar Photovoltaic (PV) installations are increasing at a very high pace in the United States. In 2017 there are approximately one million residential solar PV installations in the US. A significant share of these installations are downstream of distribution transformers and thus connected to the secondary. To precisely analyze voltage variations induced by PV systems into distribution systems, accurate models of load and PV systems connected to the secondary side of distribution transformers are required. In the work here we consider two secondary circuit modeling approaches, simple secondary and detailed secondary models. In simple secondary models all loads and all PV generators below a distribution transformer are modeled as an aggregate load and an aggregate PV generator. In the detailed secondary models all loads and PV systems below the distribution transformers are modeled individually and secondary conductors and service drops are also modeled. Using a cloud motion simulator, it is observed that employing the simple secondary models can lead to inaccurate and conservative results. Moreover, the locations with the greatest voltage changes are different in the two modeling approaches. This paper highlights the importance of utilizing detailed secondary models over simple secondary models in analyzing PV generation. / Master of Science / Power system planners and operators rely on computer-based modeling and analysis of the electric grid to ensure that electricity is delivered to consumers in a reliable manner. The current modeling is done either to simulate the high voltage transmission networks, or the primary distribution networks. Till now these modeling approaches have worked well as the electricity flow in the electric grid is largely unidirectional, i.e. power flows from the transmission network to the distribution network. Neglecting the secondary distribution network topology in such a structure of the electric grid does not introduce significant calculation errors. However, the rapid growth of residential solar PV based distributed generation over the last few years, which is expected to continue into the foreseeable future, has motivated the need to rethink this modeling and analysis paradigm. As the penetration levels of distributed generation increase, there will be bi-directional flow of electricity between the transmission and distribution networks. Accurate analysis of such a decentralized electric grid cannot be performed if secondary distribution network topology is neglected in the models. So, to precisely analyze voltage variations induced by PV systems into distribution systems, accurate models of load and PV systems connected to the secondary side of distribution transformers are required. This thesis highlights the importance of using detailed models of secondary distribution.