Solid-state instantaneous trip device for a current limiting circuit breaker

Abstract From the Canadian patent

An instantaneous solid-state trip device has two threshold values providing an upper and a lower tripping threshold. A current increase rate detector determines when a short-circuit, occurs, the prospective peak current value and if the peak, value corresponding to the electrodynamic withstand of the circuit breaker is liable to be exceeded causes a change of, threshold to bring about tripping as soon as the lower, threshold is exceeded. This high-speed tripping favours shortcircuit current limiting. When a short-circuit of a lesser importance occurs, the current variation is lower and the instantaneous trip release only trips when the upper threshold is exceeded. In most cases, this upper …