Performance analysis of the RC clampers in switching off no load arc furnace transformers
This paper presents an over-voltage attenuation performance analysis of RC clampers and surge arresters during transients caused by switching off a no load transformer applied to an arc furnace. A Brazilian Industry actual system was simulated using the Matlab/Simulink software. The simulation results indicate that the adequate use of RC clampers can reduce the arresters operations and practically eliminates the re-strikes and repetitive transient over-voltages when using vacuum circuit breakers to switch the arc furnace transformer.
RC filter to protect industrial arc furnace transformers during switching-off
It is really important to correctly design the devices that will protect the transformer from overvoltages and voltage oscillations that can occur at the arc furnace transformer terminals. These devices, the RC filters and the surge arresters, are employed to smooth dangerous over-voltages that could severely damage the transformer insulation system. 
 
The over-voltages usually happen during switching on and switching off operations, that in this kind of application occur very frequently (up to one hundred times per day). 
 
Another important task of transformer protection devices is to prevent current re-striking when interrupting the circuit and the consequent voltage escalation phenomenon. The purpose of the following study is to discuss the problem of switching off transients concerning industrial electric arc furnace transformers, particularly regarding the eventuality of breaker re-striking during the switching operation. 
 
This study demonstrates the necessity of simulating the plant circuit transient in order to determine the right protection devices as RC filters for furnace transformers.
Transient overvoltages in low-voltage systems-a field study in Germany
The "Overvoltage Measurements" field study was undertaken with the aim of establishing regulatory measures based on information from metered transient overvoltages occurring in low-voltage networks, installations, and telecommunication lines. Some 40 companies and institutions from industry and the power-utility, insurance, telecommunications, and research sectors contributed to the study. The overvoltages occurring between phase conductors and protective conductors were also measured.