Application - ABB RELION REX640 Technical Manual

Section 9
Control functions
9.11.7
9.11.8
1588

Application

PASANCR is a numerical automatic controller for arc suppression coil (Petersen coil)
and the parallel resistor. It can be applied to compensated networks where a switched
parallel resistor is optionally connected in parallel with the arc-suppression coil. An
efficient protecting method against earth faults occurring in a medium-voltage
compensated network is the earth-fault compensation. It is carried out by inserting an
inductive coil (arc suppression coil or Petersen coil) between the transformer's star
point and the earth in order to compensate the zero-sequence capacitive current of the
network. It increases the probability of the arc extinction in case of a temporary earth
fault. The arc extinction coil is effective only if its value is tuned to the zero-sequence
capacity of the network so they are in resonance state and as a consequence the earth-
fault current is very low.
Commissioning
During the coil setup process, it is not yet needed to connect the ASC to the network.
The coil setup consists of two parts:
• Calibration of coil
• Evaluation of coil linearity
The coil calibration procedure is started by activating ST_CALIB input which can be
done via local HMI application. Before starting the procedure, it must be checked that
coil end switches (HIGH_LIMIT and LOW_LIMIT) are connected to the controller.
If end switches are not available, end positions are detected during the calibration
process if there was no coil movement for more than 20 s.
First, in the coil calibration procedure the coil is moved automatically from the lower-
end switch to the upper-end switch. In both locations, the corresponding
potentiometer values are recorded for further use. Also, the coil movement speed is
determined during the calibration procedure. Secondly, the coil is moved to its middle
position and the after-running and mechanical play of the coil are determined. Finally,
the potentiometer gaps are determined. All results from coil calibration (running
speed, after running, mechanical play and potentiometer gap locations) are visible in
the Monitored data view.
After the calibration, the coil linearity is evaluated. The automatic coil calibration
determined the potentiometer ohmic end-switch values. These values are displayed on
the HMI and can be entered into the linearization table. The corresponding coil
position values (that is, inductive current of the coil) might be entered, for example,
from the coil routine test report delivered by the coil manufacturer. The values are
entered at coil nominal voltage level which is defined with Coil V Nom setting.
Moreover, if the potentiometer/coil position relationship is nonlinear, additional eight
interpolation points, or part of them, might be applied. This is done by entering the
potentiometer and corresponding coil position values into the linearization table.
Values which are left to default value of 0.0 are discarded from the actual linearization
curve. Both end values of the linearization table are displayed on the HMI view of the
1MRS759142 C
REX640
Technical Manual