Arc-circuit interaction including the effect of pre-current zero arc instability

A computer arc model is developed which is capable of predicting the point of arc instability and simulate the subsequent current chop. It can also determine the level of current chopped and the response of the system to the phenomenon. The model is inserted in a computer algorithm which uses the conductance of the arc and the nodal equations of the electrical system to which the interrupter is connected to compute the arc voltage and current at every time interval. The level of current chopped (i sub ch) at different values of the line-side breaker capacitance CG is determined. The resulting graph of 1 sub ch vs CG is compared to results obtained experimentally, which qualitatively verifies the validity of the model. A theoretical comparison is made between connecting the capacitance from the line-side breaker terminal to ground versus connecting the same value of capacitance directly across the breaker contacts. The model predicted no significant difference in arc stability between the two configurations. However, pertaining to the transient recovery voltage (TRV) the position of line-side breaker capacitance CG produced less severe TRVs at low values of capacitance when compared to the same capacitance connected across the gap. The converse was true at higher values of capacitance.