Due to the large and rapid increase in the demand for electricity and the gradual decline of non-renewable sources of energy (fossil fuels, etc.), the performance of electrical systems has to be developed so the use of distributed generation and its connection with the main networks is one of these methods but this linkage causes some problems like changing in electrical voltage. In this research a radial electric distribution system was simulated and studied the effect of distributed generation on electrical voltage stability -in static and dynamic state-and its effect when the generator is synchronous or induction.