Why in the early days the relay is not used in the power system?

Question

Why in the early days the relay is not used in the power system?

Answer 1

When were the "early days"? What sort of power system?

Relays were and are used a lot. Problems with relays are often related to the maintenance of the contacts. Particularly in power systems, when the contacts of a relay open a substantial arc can form and the arc often damages the surface of the contacts. Once the contacts start to become pitted, the relay may not make good contact when it closes the next time, so the system becomes unreliable.

In heavy power systems, the problem with arc formation is so serious that specially designed "arc chutes" are built to help kill the arc, along with high pressure nitrogen blasts. At that level though they're no longer called relays, but "contactors" and "switchgear".