The sudden pressure relay is an instrument designed for responding to a sudden increase of pressure, usually generated by an internal fault of the transformer. It reacts quickly and has a micro switch that can be connected to the breaker trip, to reduce damage in the transformer tank.
The mechanical rapid pressure relay is used in combination with a seal-in relay to maintain the alarm and trip circuits active, when the momentary contact of the SPR operates. This condition remains until the reset button of the seal-in relay is pressed to return the device to its initial condition. A red LED located in the upper right part of the device lights on, while the seal-in relay is in the alarm or trip condition.
This device also responds to slow pressure rise and includes a SCADA switchable output (0-1 mA or 4-20 mA) for the remote monitoring of the transformer tank pressure. It also includes an additional relay that is activated by a certain pressure level adjustable by the user. It is composed of two main parts: apressure sensor and a control panel.