Superconducting liquid nitrogen insulated metal enclosed switchgear
Gas insulated Metal enclosed Switchgears (GISs) are widely applied in electric power industry for transmission and distribution of electric energy because of the good dielectric and interrupt properties of SF6. However, the widespread use of SF6 may have a bad effect on the atmosphere and causes global warming effect. This paper present an eco-friendly switchgear: superconducting liquid nitrogen insulated metal enclosed switchgear (LNIS). This switchgear mainly includes superconducting fault current limiter (SFCL), vacuum circuit breaker, disconnector, earthing switch, measuring system, arrester, bus bars, liquid nitrogen circling and cooling system. In this LNIS, the current-limited-interruption will be applied. When short circuit fault generates, the short circuit current will be limited immediately by SFCL and vacuum interrupter can interrupt the current more easily. Besides the good dielectric property, the low temperature property of liquid nitrogen can helps the switchgear against the thermal shock brought by impulse current and short circuit current. At last, a brief estimation about the power and cost considering liquid nitrogen circling system and cooling system is discussed.