Zones of Protection

In power systems, the entire setup is divided into protective zones. If a fault occurs within a zone, it is isolated, protecting the rest of the system.

These zones include generators, transformers, buses, transmission and distribution lines, and motors. Think of these as different rooms in a house, each protected by its circuit breaker.

Each room or zone is defined by a closed dashed line. Inside each room, there could be one or more components.

The unique characteristics of these protective zones include overlap and circuit breaker placement. Circuit breakers are like guards standing at the intersection of these rooms, isolating any room that encounters a problem.

So, if a fault occurs in the kitchen, all circuit breakers linked to the kitchen will open, isolating it and preventing the fault from affecting other rooms.

Overlapping zones ensure no area is left unprotected by having two doors between adjacent rooms, so if one fails, the other can still protect.

Overlap is achieved using two instrument transformers and relays for each circuit breaker.