Accessories
13.2 Accessories for 3UG4 monitoring relays
3UG4 / 3RR2 monitoring relays
Manual, 05/2016, NEB927043002000/RS-AC/004
339
13.2.5.3
Potential for optimization
Potential for optimization in the event of extremely high currents, false tripping due to high starting
currents or in environments with high EMC interference
1.
Extend the ON-delay time to fade out fault currents measured during motor startup.
2.
Extend the tripping delay time to prevent false tripping due to EMC interference.
3.
Select a residual current transformer with a larger internal diameter. The reduced
magnetic field strength that passes through the transformer due to the extended distance
between power cables and transformer reduces the measuring accuracy but also the
susceptibility to interference.
4.
Route the transformer connecting cables at a greater distance to live cables
5.
a) Using solid shield sleeves or wound shield sleeves made of soft iron sheet metal may
be advisable to be able to monitor for small fault currents at extremely high rated
currents.
We recommend using a soft iron sheet metal shield with a thickness of 0.1 mm at
minimum and fold it around the cable bundle several times so that the overall shield is
1 mm at minimum. The shielding sleeve length (L) must correspond to the internal
diameter of the transformer used.
①
Phase (and neutral conductor)
②
Shield sleeve
③
Residual current transformer