using intelligent trip units for NSX , NS and NW CB with high current harmonics in the network

[Kareem]

Hello

we have case to use intelligent trip unit with NSX , NS and NW with harmonic order in the network up to the 31 order. Would the harmonic cause malfunction trip or it will work smoothly , meanwhile if we connected supply for the trip unit through DC would this overcome the malfunction issue if it is exists.

as a hint there is harmonic filter installed at the LV MDB but sometimes it go out for maintenance so in this case the CB will have malfunction trip or what can we do .

also if the thermal magnetic trip unit affected or not by the harmonics

[geir_eas_no_bfo · Accepted solution]

Some harmonic current`s will probably cause tripping of CB`s.

But probably only if the real current  (load) is close to Ir settings, beacuse harmonics cause som invisible extra load current. If you know the harmonic current percentage, you could calculate the actual current flowing in the system I think.

BR 

GIA