• Low burden
  • Trip circuit can be supervised with breaker open or closed
  • Mis-tripping of breaker by accidental Short circuits avoided
  • No false alarms given due to protection operation
  • Manual and electrical reset

Type ETCA43 consists of three units connected as shown in follow figure .Under healthy condition with the circuit breaker closed , both units are energized . If the trip circuit become open or the supply fails , unit RL2 drops off and opens contacts RL2-1 to de energies unit RL1 . when the drops off and opens the auxiliary switch shunts contact RL2-1 to hold inunit RL1 . The units are delayed on drop off for a total of 400 ms , to prevent a false alarm due to voltage dips caused by faults in other circuits or during a normal tripping operation , when unit RL2 is momentarily short circuited by the self reset trip relay contact .If the trip relay fails to reset due possibly to failure of the circuit breaker tripping , the Alarm is initiated .When the circuit breaker is open , unit RL3 is also energized and via the normally closed auxiliary switch and unit RL1 is hold in by contact RL3-1 .unit RL3 detect trip circuit abnormalities with the circuit breaker open , in a similar manner to unit RL2 with the circuit breaker closed .

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