Issue:
Can we achieve earth fault alarm without an external sensor in 3PH4W
Product Line:
Circuit Breakers
Environment:
Masterpact MTZ, Micrologic X control unit
Resolution:
As per MasterPact MTZ - MicroLogic X Control Unit User Guide, the ground -fault current is calculated or measured as below
MasterPact MTZ - MicroLogic X Control Unit User Guide Link:
https://www.se.com/au/en/download/document/DOCA0102EN/
The basic principle of ground fault current Ig is the vectorial sum= I1+I2+I3+In.
Please see below one example for better understanding:
1. If customer is 3phase 4 wire system (with Neutral), there are two solutions of ground fault alarm/protection:
1) Customer can select 3P breaker, but breaker should be configurated as 3P+ENCT, that means the external neutral CT sensor is necessary.
2) Customer can select 4P breaker, no necessary for external neutral CT sensor.
2. If customer is 3phase 3 wire system (without Neutral):
Customer should select 3P breaker and declares the ENCT to “NO”, no necessary for external neutral CT sensor.
Anyway, if there is neutral phase in customer system, neutral current should be measured in 4P or 3P with external sensor.
Can we achieve earth fault alarm without an external sensor in 3PH4W
Product Line:
Circuit Breakers
Environment:
Masterpact MTZ, Micrologic X control unit
Resolution:
As per MasterPact MTZ - MicroLogic X Control Unit User Guide, the ground -fault current is calculated or measured as below
MasterPact MTZ - MicroLogic X Control Unit User Guide Link:
https://www.se.com/au/en/download/document/DOCA0102EN/
The basic principle of ground fault current Ig is the vectorial sum= I1+I2+I3+In.
Please see below one example for better understanding:
1. If customer is 3phase 4 wire system (with Neutral), there are two solutions of ground fault alarm/protection:
1) Customer can select 3P breaker, but breaker should be configurated as 3P+ENCT, that means the external neutral CT sensor is necessary.
2) Customer can select 4P breaker, no necessary for external neutral CT sensor.
2. If customer is 3phase 3 wire system (without Neutral):
Customer should select 3P breaker and declares the ENCT to “NO”, no necessary for external neutral CT sensor.
Anyway, if there is neutral phase in customer system, neutral current should be measured in 4P or 3P with external sensor.
Released for:Schneider Electric New Zealand
