ABB REG670 - Page 189

Compensation for earth -return path for faults involving earth is done by setting the
parameter KN and KNAng where KN is the magnitude of the earth -return path and
KNAng is the argument of the earth-return path.
0 1
1
3
Z Z
KN
Z
-
=
×
IECEQUATION14023 V1 EN (Equation 35)
(
)
0 1
arg
3 1
Z Z
KNAng
Z
-
=
×
EQUATION1580 V1 EN (Equation 36)
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-earth and phase-to-phase measuring loops can be time delayed
individually by setting the parameter tPE and tPP respectively. To release the time
delay, the operation mode for the timers, OpModetPE and OpModetPP, has to be set
to On. This is also the case for instantaneous operation. In instantaneous case, the
timers tPE and tPP need to be set as zero.
The operate timers triggering input depends on the parameter ZnTimerSel setting. The
parameter ZnTimerSel can be set to:
• Timers separated: Phase-to-earth and phase-to-phase timers are triggered by the
respective measuring loop start signals.
• Timers linked: Start of any of the phase-to-earth or phase-to-phase loops will
trigger both the phase-to-earth or phase-to-phase timers.
• Internal start: Phase-to-earth and phase-to-phase timers are triggered by the
INTRNST input.
• Start from PhSel: The phase-to-earth and phase-to-phase timers are triggered by
the STCND and LDCND inputs. Each of the two inputs consist binary status
information related to the six measuring loops. Hence if any of the measuring
loop status is high in both two inputs STCND and LDCND, then the timers will be
triggered. In case when LoadEnchMode is off then only STCND enables the timer.
It is not recommended to use this timer setting for the Zone
instance where LoadEnchMode is off.
• External start: Phase-to-earth and phase-to-phase timers are triggered by the
EXTNST input.
1MRK502052-UEN B Section 7
Impedance protection
183
Technical manual