Ground Fault Protection - engineering site - Schneider Electric

As soon as the network has at least 2power supplies, the protection systemdecided upon must take into accountproblems linked to:b third order harmonics and multiplesof 3b the non-breaking of the neutralb possible current deviations.Consequently, the study of a“multisource” diagram must clearly showthe possible return paths :bIn shortof the neutral currentsof the insulation fault currentsbi.e. clearly distinguish the PE and thePEN parts of the diagram.3.3.3. Application: implementation in a multisourceTN-S systemThe multisource case is more complex.A multiple number of network configurations is possible depending on:b the system (parallel power sources, normal / replacement power source, etc.)b power source managementb the number of neutral earthings on the installation: the NEC generallyrecommends a single earthing, but tolerates this type of system in certain cases(§ 250-21 (b))b the solution decided upon to carry out the earthing.Each of these configurations requires a special case study.The applications presented in this paragraph are of the multisource type with2 power sources.The different schematic diagrams are condensed in this table.Switchgear PositionOperation Q1 Q2 Q3Normal N F F OReplacement R1 O F FReplacement R2 F O FC: ClosedO: OpenThe 6 criteria (a 0, a 1, a 2, b 1, b 2 and b 3) to be applied to each system are definedin paragraph 3.2.1.To study all case figures and taking into account the symmetry between GFP1 andGFP2 devices, 12 criteria must be verified (6 criteria x 2 systems.DB117246Diagram 24 - coupling23