chapter  14
26 Pages

Three-Phase and Distribution System Load Flow

WithJ.C. Das

A single-phase positive sequence network of a three-phase system is adequate for balanced systems. During faults, though the systems are balanced, voltages are not. Unbalance voltages and unbalance in three-phase networks can also occur simultaneously. The cogenerators in distribution system load flow are not modeled as PV type machines, that is, to control the bus voltage. For load flow the synchronous generators can be modeled as constant complex power devices. A distribution system forms a ladder network, with loads teed-off in a radial fashion. The optimum location of capacitors in a distribution system is a complex process. The two main criteria are voltage profiles and system losses. A three-phase load flow study is handled much like a single-phase load flow. Using the system in the phase frame of reference, a generalized analysis of the power system network can be developed for unbalance, that is, short-circuit or load flow conditions.