The ABB Sudden Pressure Relay is a device that detects a sudden rise in gas pressure within a power transformer and forces a microswitch to temporarily change state. Such a pressure increase would likely be caused by arcing within the transformer - a critical condition. Ordinary pressure changes due to loading or environment are not detected by the SPR.
An optional Seal-in Relay may be used to capture and hold the signal from the momentary switch to indicate an SPR trip. Terminal blocks allow cable connection from the relay to auxiliary equipment. A manual reset button on the Seal-in Relay clears the trip status.