Superconductive Magnetic Energy Storage (SMES) is one of the effective measures to suppress system instabilities in electric power networks because of its fast response at exchanging electric power. Two types of experiments, dynamic and transient, have been performed to suppress instabilities by using an SMES unit on a model power system. The test system has a 60 kVA synchronous generator, a double-circuit transmission line connected to an infinite bus, and an SMES unit with an SCR converter. They simulate a salient pole synchronous generator of 600 MVA and a transmission line of 275 kV with 380 km in length. The SMES unit whose maximum stored energy is 100 kJ can exchange energy matched with the model system. The SMES unit could effectively suppress these instabilities by exchanging energy.