MBR – Membrane/Bag Rupture Relay

The Membrane/Bag Rupture Relay – MBR is a device capable of detecting the rupture of the rubber membrane or bag used in oil preservation systems on power transformers and reactors.

The MBR is comprised of an optical sensor that must be mounted on the membrane or inside the rubber bag (on the air side), and a control unit located in the transformer control cabinet.

The sensor is provided with a poly-sulphur capsule containing a emitting LED and a trigger circuit. The control unit has a change over contact and two LED’s, one to signal the membrane or bag rupture, and another to signal the operational status.

The MBR operation is based on the principle of light reflection. When there is no oil present, the light produced by the emitting-LED is completely reflected internally by the capsule dome and captured by the optical receiver. If the oil covers the capsule, the reflection effect on the dome is restricted. The rupture causes part of the emitted light to disperse in the oil, and theamount of light that reaches the optical receiver is reduced. This change in light refection causes the unbalancing of the coupling circuits and the actuation of the signal contact.

The output contact is reversible, and its operation mode (operate or return to rest mode in case of membrane failure) is selected bymeans of an external jumper.

The auxiliary supply voltage to the MBR can be in the range 85 to 265 Vdc/Vac 50/60Hz, covering all auxiliary voltages commonly found in powerplants. Electrical insulation is provided between input, output and auxiliary supply circuits.