ABB REL650 series Technical Manual page 117

1MRK 506 335-UUS A
Technical manual
Z0-Z1
KNMag =
×
3 Z1
EQUATION1579 V1 EN
( )
Z 0
=
KNAng ang
3
EQUATION1807-ANSI V1 EN
where
Z0 is the complex zero sequence impedance of the line in Ω/phase
Z1 is the complex positive sequence impedance of the line in Ω/phase
The phase-to-ground and phase-to-phase measuring loops can be time delayed
individually by setting the parameter tPGZx and tPPZx (where x is 1-5 depending on
selected zone) respectively. To release the time delay, the operation mode for the timers,
OpModetPGZx and OpModetPPZx (where x is 1-5 depending on selected zone) has to be
set to Enabled. This is also the case for instantaneous operation.
Theory of operation
The mho algorithm is based on the phase comparison of a operating phasor and a
polarizing phasor. When the operating phasor leads the polarizing phasor by more than 90
degrees, the function operates and gives a trip output.
Phase-to-phase fault
Mho
The plain mho circle has the characteristic as in figure 41. The condition for deriving the
angle β is according to equation 15.
( )
β =
V − I ⋅ Z −
arg arg
AB AB
EQUATION1789-ANSI-650 V1 EN
-
Z 1
×
Z 1
( )
V
pol
Section 6
Impedance protection
(Equation 13)
(Equation 14)
(Equation 15)
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