Theoretical expression of rate of rise of recovery voltage across a circuit breaker connected with fault current limiter

The present paper looks at the mathematical expression of the rate of rise of recovery voltage (rrrv) across a circuit breaker connected with fault current limiter (FCL) as a function of the limiting impedance ZFCL and the limited current when a fault occurs at a distance near the load-side terminals of the FCL. The FCL in current-limiting operation was assumed to have a limiting element composed of either an inductance or a resistance. In the model of the inductive FCL, a capacitance Cp consisting of a coil stray capacitance and a necessary additional capacitance was taken into account. Using the mathematical expression of the relationship between the rrrv and the limited current enables us to find out the dependence of the interrupting duty on circuit parameters. Unlike the resistive FCL where the rrrv is linearly proportional to the limited current, the rrrv for the inductive FCL depends not only upon the limited current but also on the capacitance Cp and the stray capacitance CFCL of the FCL to the ground. Depending upon the kind of the FCL, the parameters of the FCL and the system, the general expression of the rrrv makes it possible to estimate the increasing or decreasing percentage of the rrrv across a circuit breaker connected with FCL.