Cross Jet

Read this may help

During closing and interruption the arc damages the tip of the contacts. If these are used as main contacts then there will be significant contact resistance and that will be permanent (or rather deteriorating with each make and break)

The sacrificial contacts are used for this purpose, these rods are the first to come in contact and the last to break it. As a result all the damages take place in these, leaving the main contacts relatively undamaged.

BTW: one must not use acronyms, it took a moment to realise OCB is oil circuit breaker. The crss jet confused , since there are other more probable areas for it. Then the sacrificial contacts made the spark.

UD15

To give it it's proper name the "cross jet explosion pot"* controls the arc in an OCB. The sacrificial contacts work in conjunction with it. The contacts are the moving and the fixed. The fixed are rose type IE arranged in a circle, the moving is a round nosed rod (very often referred to as the candle). The rose contact may have 4, 5 or 6 contacts depending on the current rating, one contact will be a fraction longer than the others, and this is the sacrificial contact. First to make, last to break.
The pot fits closely around the rose, it has a orifice at the bottom which is a close fit around the candle. To one side a passage in the wall of the pot leads from the top camber to near the middle of the orifice. Opposite the passage in the orifice is a series of slots.
On opening the OCB the candle moves downwards, on parting with the sacrificial contact the arc is struck. The arc generates gas, which collects in the top chamber forcing relatively cool oil down the passage forcing oil across the path of the arc as it passes the slots. This movement of oil extinguishes the arc.

During maintenance the sacrificial contact is usually changed and the candle rotated to present a new face to the sacrificial contact.

*Reyrolle refer to them as turbulators.