Restrike voltage

Okokura. K.Y.. Multiple restriking voltage efteci in a vaeuiim circuit breaker on motor insulation, IEEE Paper 80. SM 697-3 (1980). 

A line switch (LS) or a disconnector (DS) is used in a substation to interrupt a voltage. Because the operating speed of LS/DS is slow in general, it cannot be modeled as a time-controlled switch like a CB. Instead, the LS/ DS is modeled as a voltage-controlled switch so as to be able to consider a restriking voltage during a transient. 

As a result of a better insulation and insulating medium of an LT interrupting device, compared to its voltage rating, there are no restrikes of the contact gap after a current zero. The TRV is insufficient to establish an arc. 

By the immediate first current zero it is assumed that the contacts have travelled sufficiently apart to achieve the required deionization and have built up adequate dielectric strength to withstand at least 0.95 V, . If the circuit does not interrupt at the immediate current zero at a which is so near to the point of chopping Vt , the interruption will take place only by the next current zero at point h and result in another 260 strikes by then. To study more accurate behaviour of an intenupter, with the number of restrikes and the formation of the actual transient voltage waveforms on current chopping, oscillograms similar to those during a short-circuit test may be obtained (Section 14.3.6). 

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... 

Figure 23.5 Build-up of capacitive voltage (TRV) on restrike during contact interruption in a grounded star HT capacitor unit...

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