This FAQ has been written for NEAL (North East Africa and Levant) region. If you are looking for information for another region, please select the correct country from the top-left dropdown in the page and 'Navigate to Browse FAQs' in the Support menu.
Can we install Earth Fault protection for a Three pole ACB with micrologic 6 or 7 trip unit without external Neutral CT?
There are two types of ground-fault protection:
1- Residual:
The function determines the zero-phase sequence current, i.e. the vector sum of the phase and neutral currents
2- Source Ground Return:
Using a special external sensor, this function directly measures the fault current returning to the transformer via the earth cable.
In case of 3 pole breaker (4-wire system), for ground-fault protection, it is mandatory to install an external CT for calculating the current to ground, thanks to a vectorial sum of phases and neutral currents. While for the 4 pole CB, it is not mandatory to install an external CT.
1- Residual:
The function determines the zero-phase sequence current, i.e. the vector sum of the phase and neutral currents
2- Source Ground Return:
Using a special external sensor, this function directly measures the fault current returning to the transformer via the earth cable.
In case of 3 pole breaker (4-wire system), for ground-fault protection, it is mandatory to install an external CT for calculating the current to ground, thanks to a vectorial sum of phases and neutral currents. While for the 4 pole CB, it is not mandatory to install an external CT.
Released for: Schneider Electric Egypt and North East Africa
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