I would wish to have an expert explain to me the difference between ANSI51N and ANSI51G both at the physical level and configuration ? GROUND FAULT PROTECTION ANSI 51n/g

ANSI codes used in Masterpact MTZ Catalog are based on “IEEE ANSI C37.2 2008 IEEE Standard for Electrical Power System Device Function Numbers, Acronyms, and Contact Designation”

This standard defines this device function number as : “A device function number, with an appropriate prefix and appended suffix (or an acronym), is used to identify the function(s) of each device installed in electrical equipment. These numbers and acronyms are to be used in drawings, elementary and connection diagrams, instruction books, publications, and specifications.

This standard is not defining any kind of performance or operating ranges of functions. It is just a codification, historically coming more from HV installation in north America so it is not always fitting well with IEC Low Voltage.

- We have selected 51N (C37.2 96) or 50N-TD/51N (C37.2 2008) for the “G” function of micrologic 6 when Ground fault protection is based on summation of individual current transformers of lines and neutral current.

Micrologic 6 “G” protection can be used with external sensor connected on neutral to earth link (“SGR”) in that case the codification is not the more suitable but this case is not the most common.

- We have selected 51G(C37.2 96) or 50G-TD (C37.2 2008) for the Residual earth leakage “Vigi” function as we do in our MV ranges such as Sepam or Easergy when Ground faut protection is based on a dedicated toroid directly measuring the earth fault current.

They could be both called 51G but in IEEE ANSI C37.2 2008 Section 3.5.3 in the Definition of “G” and N there is a note 3 saying :

Note 3 The suffix N is preferred when the device is connected in the residual of a polyphase circuit, is connected across a broken delta, or is internally derived from the polyphase current or voltage quantities. The suffix G is preferred where the measured quantity is in the path to ground, or, in the case of ground fault detectors, is the current flowing to ground. See Figure C.2 in Annex C for examples.

We are using the same type of codification MV ranges such as Sepam or Micom, Easergy Pxx and Competition seems quite close too.

Publié pour:Schneider Electric Belgium