Experiment and simulation of PTC used in fault current limiter

Positive Temperature Coefficient thermistor (PTC) is a key component of fast switch fault current limiter (FCL). Nickel wire is usually selected as PTC for FCL. The mass of the nickel must be big enough to absorb the energy due to the short circuit current, otherwise the temperature will reach melting point of Nickel. But big mass means high costs and big device. Compared with nickel, the resistivity of ceramic PTC and polymer PTC increase rapidly with temperature rising. In this paper, ceramic PTC and polymer PTC samples from different producers were tested to find the best one for FCL application. Parameters such as cold resistivity, curve of resistivity against temperature, breakdown voltage, and performance at pulse current were tested. At last a simulation of FCL in power system is done with the parameters of the best PTC samples. It is proved by the simulation results that the existing ceramic PTC and polymer PTC could not meet the requirements of FCL. For ceramic PTC, the cold resistivity and specific heat capacity must be decreased; breakdown voltage needs to be enhanced. For polymer PTC, breakdown voltage needs to be enhanced; specific heat capacity needs to be decreased.