GE MiCOM P40 Technical Manual page 119

P446SV
where:
Z is the total zero sequence impedance of the line (a complex value)
●
L0
● Z is the total positive sequence impedance of the protected line (complex value)
L1
Z is the zero sequence mutual impedance between the two circuits (complex value).
●
m0
If used, you must set the mutual compensation feature k
kZm Mutual Set (the absolute value) and
●
kZm Mutual Angle (the angle in degrees).
●
Note:
The following paragraph applies only to distance products and so may not be applicable to your model
In applications where the Mutual Compensation is used to reduce errors in the distance elements, a third setting,
Mutual Cut Off, is used for a fast dynamic control. The ratio I
the ratio is higher, mutual compensation is suppressed to prevent false-tripping for faults on the parallel line.
Typically a Mutual Cut Off factor of 1.5 is chosen to give a good margin of safety between the requirements of
correct mutual compensation for faults on the protected circuit whilst avoiding maloperations for faults on the
parallel circuit.
P446SV-TM-EN-1
using the settings:
Zm
/I is compared with the Mutual Cut Off setting. If
M N
Chapter 5 - Configuration
87