Why do we use isolators on both sides of the circuit breaker?

In over head line feeders isolator(Air Break Switch) is provided for safety,the AB Switch opened is seen physically.So any conversent personnel can work boldly.

Thiagarajan.e

In Line feeder it must be Isolated for both sides for the purpose of maintenance of the circuit breaker and power line also

but in transformer we may find transformer with only bb isolators because when transformer is offline & earthed well there are no need for Q9 for maintenance but if exit it better for safety

In order to isolate it from either side because normally a  breaker can b catered from either side and electric current can flow through it in either direction, since we don't know which side is and which one is not energized, so to avoid this thing we isolate it from either side to ensure breaker is fully isolated, further safety is ensured by closing each side's earth switch

TO ISOLATE THE FAULTY ELEMENTS FROM THE POWER SYSTEM WHEN THERE IS ANY FAULT.