Varistor

Owing to the surge in demand for electrical energy and increase in penetration of Diesel Generators, an increase in the fault level of the power system is being observed. The employment of the FCL (Fault current limiter) has been one of the most efficient techniques for the control of fault current in recent times. This paper introduces and describes a solid-state fault current limiter which is controlled by an Insulated Gate Bipolar Transistor (IGBT). The complete design and analysis have been discussed. The simulation is done with MATLAB/Simulink software.

In this study, a durability model for predicting the lifetime of MOV devices used to prevent DC switch damage due to occasional switching surges is proposed and validated. In addition, MOV devices are subjected to induced switching DC surges of a constant amplitude and variable time durations. Each MOV of the 270 selected devices sourced from three different manufacturers with similar size and electrical specifications was subjected to 5000 degrading surges. Three samples of 30 of the selected MOV devices from each manufacturer were degraded by induced switching DC surge durations of 2, 3, and 4 ms in order to reach an undesirable degradation level of 10% change in V1 mA. A statistical analysis of the three MOV manufacturer sample averages of the accumulated conduction charge transfer at 10% change in V1 mA supported the proposed durability model irrespective of the surge charge content variation and MOV material differences. The results show that MOV device durability or resilience...