8 MB - POWERLAB

Electrical diagrams Masterpact NT and NW 0Earth-fault and earth-leakage protectionNeutral protectionZone selective interlockingEarth-leakage protectionConnection of the rectangular-sensor secondarycircuitUse the cable shipped with the rectangular sensor.DB101415Neutral protectionb three pole circuit breaker:v Masterpact equipped with Micrologic P or Hv the current transformer for external neutral isnecessary (the wiring diagram is identical to the oneused for the residual earth-fault protection)b four pole circuit breaker:v Masterpact equipped with Micrologic A, P or Hv the current transformer for external neutral is notnecessary.Zone selective interlockingZone-selective interlocking is used to reduce theelectrodynamic forces exerted on the installation by shorteningthe time required to clear faults, while maintaining timediscrimination between the various devices.A pilot wire interconnects a number of circuit breakers equippedwith Micrologic A/P/H control units, as illustrated in the diagramabove.The control unit detecting a fault sends a signal upstream andchecks for a signal arriving from downstream. If there is a signalfrom downstream, the circuit breaker remains closed for the fullduration of its tripping delay. If there is no signal fromdownstream, the circuit breaker opens immediately, regardlessof the tripping-delay setting.Fault 1.Only circuit breaker A detects the fault. Because it receives nosignal from downstream, it opens immediately, regardless of itstripping delay set to 0.3.Fault 2.Circuit breakers A and B detect the fault. Circuit breaker Areceives a signal from B and remains closed for the full durationof its tripping delay setto 0.3. Circuit breaker B does not receive a signal fromdownstream and opens immediately, in spite of its trippingdelay set to 0.2.DB101420Note: the maximum permissible distance between two devicesis 3000 m. A downstream circuit breaker can "control" up to tenupstream circuit breakers.95