A switch, circuit-breaker, or other tripping device that operates when the current in a circuit exceeds a predetermined value. A current that causes the release to operate is an overcurrent.

The device is often designed so that a delay occurs after the overcurrent is sensed and before the device trips. Several different delay conditions can be used: definite time lag overcurrent release has a predetermined delay independent of the magnitude of the overcurrent; inverse time lag overcurrent release has a delay that is an inverse function of the magnitude of the overcurrent; inverse and definite minimum time lag overcurrent release occurs when the delay is an inverse function of the magnitude of the overcurrent until a minimum value of the delay is reached. Compare undercurrent release.