The maximum instantaneous input current that is drawn by an electrical device when it is first turned on, is defined as overvoltage current, also known as the input current or overload current. The startup current may be as high as 100 times the normal steady state current and lasts less than half of a normal 60 Hz cycle.
An element, an intermetallic alloy or a compound that will conduct electricity without resistance below a certain temperature. Dutch physicist HEIKE KAMERLINGH ONNES of the University of Leiden was the first person to observe superconductivity in mercury. Superconductivity is a phenomenon of zero zero resistance certain materials when cooled below a critical temperature characteristics.
Systems designed to use superconductors to limit fault currents in electrical networks are being tested. The authors describe superconducting fault current limiter (SCFCL) that can be classified into resistive or shielded core types. The characteristics and operation of each type of device are described. Both the shielded type and the resistive types of SCFCL use the same amount of superconducting material to achieve a given limiting behavior. This is because the nominal power per conductor volume is determined by the product of the field induced by failure and the critical current, which is the same for both devices, assuming that the same type of superconducting material is used. The shielded core limiter only operates on alternating current and is much larger and heavier than the resistive SCFCL. While only one large program remains in the low-temperature SCFCL type, more than 10 major projects are underway worldwide in the high-temperature type of the device. The main reason is the lower cost of HTS cooling.