Dynamic equivalents of distribution systems, including the dynamics of elec
tric loads and online tape changers, are needed in voltage stability studie
s. A method for a dynamic equivalent of a radical distribution system for v
oltage stability studies and an equivalent model are proposed. The procedur
e and detailed formulas for separate aggregation of dynamic loads and netwo
rk with OLTCs are derived. Case studies show the accuracy of the equivalent
model and the availability of the method.