bonding two buildings with separate service
My brother has a house and a barn about 150 feet apart, each with separate electrical service. I believe they are both served from the same POCO transformer. He intends to install a LAN between the two buildings, which will amount to trenching and running some CAT-5.
My question is: "Does he need to bond the two buildings together to reduce the risk of his CAT-5 becoming an electrical pathway for imbalances?".
If so, how do you determine what size wire is necessary?