Post-arc current measurement down to the ten milliamperes range

A novel post-arc current measuring shunt is described. This shunt employs parallel connected diodes to automatically insert and disconnect the measurement resistance, very close to the current zero. The realized precision and sensitivity allow reproducible measurements down to tens of milliamperes range, with about a 5 MHz bandwidth. Furthermore repetitive testing with main currents of up to 80 kA peak poses no problem with this configuration. Using this technique the authors have discovered a new type of post-arc current which can last many milliseconds without provoking circuit breaker failure. They call this the post-recovery current