This test just apply to 3 pole operation circuit breakers.
As Fig these circuits use a three-phase current source and, generally, two voltage sources. one voltage source provides the TRV for the first pole-to-clear and the other gives the recovery voltage for the second- and third poles-to-clear, in the case where these poles clear simultaneously as in non-effectively earthed systems.
This system have following components:
- a three phase current source (G)
- voltage source 1 with current injection parallel circuit connected across the first pole-to clear.
- voltage source 2, as above, connected across the other two poles in series that interrupt the current at the same moment because of the absence of earthing at the source side;
- a three-pole auxiliary circuit breaker (AB)
- a three-pole tested circuit breaker (TB)
- arc-prolongation circuits (APC) connected to each phase of the current circuit to prevent an early interruption by the tested circuit-breaker and to assure the longest possible arcing time.