Frequently, the reference node is chosen to be the node to which the largest number of branches are connected. Many practical circuits are built on a metallic base or chassis and usually there are a number of elements connected to the chassis which is a logical choice for the reference node In many cases such as in electric power systems the chassis is the earth itself
For this reason the reference node is frequently referred to as ground The reference node is thus at ground potential or zero potential and the other nodes may be considered to be at some potential above zero