Voltage surges

ANSI/IEEE-C62.41-1991 Recommended practice for surge voltages in low voltage a.c. power circuits ... 

The impulse test is basically an in-house coil insulation withstand test for surge voltages and forms a part of the test requirement for HT machines with resin-rich formed coils of 2.4 kV and above. Once the machine is assembled, such a test is unnecessary, as it may not be able to reveal deficiencies, if any, in the insulation of the coils deep inside the slots. Moreover, if a failure is noticed on the assembled machine, there is no option but to scrap the whole winding. 

Figure 17.8 Likely surge voltages that may be developed by different types of circuit breakers as a function of circuit surge impedance...

At this voltage when these two poles prestnke they cause a surge voltage at the motor terminals of... 

The same theory will apply in capacitor switching except that the interrupting current will now be leading the voltage by almost 90° instead of lagging. See also Section 23.5 to determine the amount of surge voltages and inrush currents. 

Valve or non-linear resistor In this version, a nonlinear SiC resistance is provided across the gap and the whole system works like a preset valve for the follow current. The resistance has an extremely low value on surge voltages and a very high one during normal operations to cause a near-open circuit. It is now easier to interrupt the follow currents. 

In fad. ihis energy should be less by the hysteresis loss (Seetion l.6.2A.(iv)) whieh has been ignored in the present analysis. If T, is the prospeetive peak surge voltage (TRV) in volts and C the dieleetrie eapaeitance of the eontaet gap in far.id at the instant of restrike, then the eapacitive energy J, received across the contact gap is... 

Anderson, J. G. and K. O. Tangen, Insulation of switching-surge voltages, in EHV Transmission Line Reference Book, Edison Electric Inst., New York, 1968. 

Power surge, voltage Power surge current Short circuit EMC... 

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