This paper presents a new formulation for system state estimation of passive electric distribution networks. The fundamental idea discussed here is how to obtain the state of the system at maximum demand condition using three sources of information: 1) a quasi-symmetric matrix called TRX representing network structure and topology, 2) power measurements at main feeder disconnection devices and reclosers installed in the network, and 3) Energy measurements and estimated load curve of aggregate users at distribution transformers. The method is formulated with real variables for single-phase positive sequence radially operated networks. Results of the application of proposed methodology are presented using the well known IEEE 4-Node test system.