ABB 615 Series ANSI, Technical Manual

Page: 382 / 713

1MAC050144-MB C
Section 4
Protection functions
615 series ANSI 375
Technical Manual
Figure 178: Operating characteristics of the restrained ground-fault protection
function
Figure 179: Setting range of the operating characteristics for the restrained
differential current principle of the ground-fault protection function
The Trip value setting is used for defining the characteristics of the function. The
differential current value required for tripping is constant at the stabilizing current values
0.0 < IB/In < 1.0, where In is the nominal current, and the In in this context refers to the
nominal of the phase current inputs. When the stabilizing current is higher than 1.0, the
slope of the operation characteristic (ID/IB) is constant at 50 percent. Different operating
characteristics are possible based on the
Trip value setting.
To calculate the directional differential current ID_COSPHI, the fundamental frequency
amplitude of both the residual and neutral currents has to be above 4 percent of In. If
neither or only one condition is fulfilled at a time, the cos
φ term is forced to 1. After the
conditions are fulfilled, both currents must stay above 2 percent of In to allow the
continuous calculation of the cos
φ term.
0.0
0.5
1.0
1.5
0.0 1.0
2.0
3.0
IB/In
ID_COSPHI/ In
ID
IB
TRIPPING
NON TRIPPING
Trip value