Breaking voltage is that voltage that can safely be opened by the contacts. This voltage is quite different than switching voltage. Although most specifications don’t really call out the difference. This becomes increasingly important as the switching/breaking voltage is increased above 200 volts. Typically when you close, say 400 volts, the contacts will switch this voltage along with any current the circuit is capable of offering. The event is all over after the first 50 nanoseconds. Typically, any metal transfer will occur only during this brief period. Now when you break this voltage an arc will occur and depending upon the amount of current available will sustain that arc. If you are trying to break a high current, say above 50 ma. The arc may be sustained for a sufficient amount of time to cause severe damage to the contacts. Extreme care must be exercised when breaking higher voltages with any current associated with the break.