No change.When the relay is closed ,the TR3 has acces to DC1 bus,when it is open ,dc buses are separated, and so is the TR3 from DC bus 1.
This is why,if TR1 fails inflight, and you didn't notice,cause the TR3 is back-up ,at G/S capture you're for a surprise as the DC bus 1 will be de-energized.
So the relay connects or disconnects the TR3 from DC bus1- hence the name -TR3 disconnect relay.