Fault current limiting

The more recommended practice is to ground the neutral solidly or through an impedance, commensurate with the requirements of the protective scheme and the fault current limited to a desired level. The terminal equipment and the windings of all the machines may now be designed for a voltage corresponding to the relevant GFF. 

To determine the grounding parameters, consider a generator rated for 200 MW, 15 kV and the ground fault current limited to 15 A. Considering GFF as -J3, the voltage ratio of the grounding transformer with a 220 V secondary will be... 

Superconducting electromagnets, current leads in, 23 855-856 Superconducting energy gap, 23 840 Superconducting fault current limiter (FCL), 23 867-868 Superconducting joints, 23 847 bulk, 23 844... 

Probably the most obvious application for superconductors is in the transmission of electrical power and it seems that that this is close to being a reality. There are many other potential applications in the power electrical engineering field, for example power generators, motors, transformers, leads and fault current-limiters. 

Leads and fault current-limiters Current leads and fault current-limiters are the first large scale commercial applications of Bi-based HTSs. Current leads significantly improve efficiency of liquid helium-cooled magnets. 

A fault current-limiter is a component which protects power transmission and distribution systems from surges caused by, for example, a lightning strike, fulfilling a function similar to that of a varistor (see Section 4.3.1). The limiter should be capable of reducing the fault current to a fraction of its peak value in less than a cycle. Because for this application the requirement is for low Jc, fault current limiters are already a commercial product. In the case of the lead shown in Fig. 4.58(b) the fault current is limited to a safe value within 5 ms of the arrival of the current spike . 

High-temperature ceramic superconductors are also promising for the application of fault current limiter, which protects the power transmission system from the damages caused by unanticipated power disturbances. The high-temperature superconducting current limiter has tremendous benefits of... 

FIGURE 8.1.18 Schematic drawing of inductive type high-temperature superconducting fault current limiter. 

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