I have two buildings (A + B) each with their own mains electrical supply. The buildings are about 20m from one another. Between the two buildings are the Cat6 cables (one active and two spares).
The Cat6 cable is terminated in a patching / data rack in each building.
Both buildings have their own patch panel and network switch. Building A houses the modem and router.
My concern is that I've heard having connected electrical devices / equipment, across two or more mains electrical supplies can cause issues / damage to the electrical devices / equipment due to different mains electrical supplies having different grounds / earths.
Is this a valid concern? And what can I do to rectify the issue?