Novar 1xxx KMB systems
24
For the controller to be able to start the automatic section power recognition process, the following
conditions must be met:
• controller automatic operation is not disabled (i.e. the Manual LED is dark)
• controller is in control mode, i.e. the numeric display mode is Measurement
• measurement voltage, at minimum value required, is connected
• connection mode of measurement U and I is defined (parameter 16)
If these conditions are met, the controller starts the automatic section power recognition process.
The process may have three or six steps. The controller consecutively connects and disconnects each
output in each step. While doing that, it measures the effect of connection and disconnection on total
reactive power in the power system. From the values measured the power of each section is
determined.
The following messages are shown one after another in each measurement attempt on the numeric
display:
1. Step number in format AC-n
AC-nAC-n
AC-n (n... step number).
2. Sectional power measured in kvars; the nominal power value of the section under
measurement is displayed, that is the value that corresponds to nominal voltage U
NOM
of
the compensation system as specified in parameter 18. If the metering current
transformer turns ratio has been entered (parameters 12 and 13), or, if measuring voltage
via a metering voltage transformer, the voltage transformer’s turns ratio as well (in
parameter 17), sectional power in the power system is shown (that is at the metering
current transformer primary side, or metering voltage transformer primary side). If the
metering current transformer primary side (parameter 12), or metering voltage transformer
primary side (parameter 17) is not defined, sectional power in the metering current
transformer’s, or the metering voltage transformer’s, secondary side is shown.
If the controller does not succeed in determining a section’s value, it does not show it. This condition
occurs if reactive power value in the power system fluctuates considerably due to changes in load.
After carrying out three steps, evaluation is carried out. If each measurement in the steps carried out
provides sufficiently stable results, the automatic section power recognition process is completed.
Otherwise the controller carries out three more steps.
A requirement for successful automatic section power recognition process is sufficiently stable
condition of the power system – while connecting or disconnecting a section, the reactive load power
must not change by a value which is comparable with, or even greater than, the reactive power value
of the section under test. Otherwise the measurement result is unsuccessful. As a rule of thumb, the
section values are recognized the more precisely, the lower the load is in the power system.
On successful completion of automatic section power recognition process, the controller checks
whether at least one capacitive section has been detected and, if so, it starts control. Otherwise the
controller goes to the waiting mode and after 15 minutes it starts the automatic section power
recognition process again.
Each section value recognized can be checked in the side branch of parameter 25. A positive power
value means a capacitive section, negative value means inductive section. If the value could not be
recognized, “----
--------
----” is shown. Each value recognized can be edited manually.
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