ABB RELION REX640 Technical Manual page 1584

Section 9
Control functions
1578
input even without the zero-sequence voltage trigger. The automatic tuning procedure
is also released when the controller mode is switched from "manual" to "auto".
PASANCR has an adaptive U
enable or disable the functionality. The functionality allows slow changes in
measured zero-sequence voltage and therefore reduces unnecessary tuning
operations. If the measured zero-sequence voltage does not exceed the V Res change
level setting during the time defined in V Ref adaptive delay setting, the existing
measured zero-sequence voltage is stored as a new reference voltage U
the adaptive period. The operation principle of the adaptive U
Figure 821.
Uo
V Res
change level
U
ref
V Res
change level
Uo
V Ref adaptive
delay
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Figure 821: Example of Uo fluctuation with and without adaptive U
(amplitude triggering mode)
Network parameter calculation
To explain the controller, the simplified equivalent circuit of a three-phase
distribution network illustrated in
• The real network is presented with its shunt admittances neglecting line series
impedances as their values are very small compared with the shunt admittances.
• The individual phase admittances of the network are presented with symmetrical
phase admittances whose sum equals
Y G j B
symm symm symm
= + ⋅
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feature. The V Ref adaptive mode setting is used to
ref
Unnecessary
tuning
Tuning
delay
No unnecessary tuning operations as the
Adaptive Uref
U is adjusted e.g. every 10 minutes
ref
feature
Figure 822 is used. The controller assumes that:
1MRS759142 C
at the end of
ref
feature is explained in
ref
Tuning Unnecessary
delay tuning
(V Ref
adaptive delay setting)
ref
Technical Manual
Time
Time
feature
(Equation 347)
REX640