Directional Self-Polarized Mho Characteristic For Earth Faults; Figure 35: Offset Mho Characteristic - GE MiCOM P40 Technical Manual

Chapter 7 - Distance Protection
V02711

Figure 35: Offset Mho characteristic

The two signals provided to the comparator are:
S = V - IZ'
1
S = V - IZ
2
Operation occurs when the angle between the signals is greater than 90°
3.1.3

DIRECTIONAL SELF-POLARIZED MHO CHARACTERISTIC FOR EARTH FAULTS

Characteristics of earth-fault elements can be represented in two different complex planes - the positive sequence
impedance plane (Z -plane) and the loop impedance plane (Z
1
reach in positive sequence impedance terms. The characteristic in the Z
depends on fault currents. However, the Z
especially if an injection test kit is used, which cannot apply the residual compensation to the impedance plot, or in
the case that the load blinders have to be verified.
The following diagram illustrates how a directional Mho characteristic for earth-faults is created.
112
V
I 
Z
V
I


I Z
-plane). The reach impedance setting defines the
LP
–plane representation is often more convenient for reference,
LP
 
I Z
90°

 
V I Z
-plane is generally dynamic because it
LP
P446SV
P446SV-TM-EN-1