ABB RELION REX640 - 9.11.6.3 Network parameter calculation

tuning procedure is also released when the Controller mode is switched from
“Manual” to “Automatic”.
PASANCR has an adaptive U
ref
feature. The V Ref adaptive mode setting is used
to 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
ref
at the end of the adaptive period. The operation principle of the adaptive U
ref
feature is explained in Figure 925 .
Uo
Time
Uo
Time
Unnecessary
tuning
V
Res
c
hange level
Tuning
delay
Adapve Uref
feature
No unnecessary tuning operaons as the
U
ref
is adjusted e.g. every 10 minutes (V Ref
adapve delay seng)
V Ref adapve
delay
Unnecessary
tuning
Tuning
delay
U
ref
V
Res
c
hange level
Figure 925: Example of Uo fluctuation with and without adaptive Uref feature
(amplitude triggering mode)
9.11.6.3 Network parameter calculation
To explain the controller, the simplified equivalent circuit of a three-phase
distribution network illustrated in Figure 926 is used. The controller assumes that:
• 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 Bsymm symm symm= + ⋅
(Equation 386)
(one third connected in each phase)
• The natural asymmetry in a real network is due to differences in individual phase
admittances and it is presented with an asymmetry admittance concentrated
into phase A and presented with admittance
Control functions
1MRS759142 F
1736 REX640
Technical Manual