KMB NOVAR 2600, Operating Manual

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NOVAR 2600 Operating Manual
4.3.1.8 Choke Control
The instrument allows connecting chokes for power system decompensation. The decompensation
system can be built as combined, in which case both chokes and capacitors are connected to the
controller, or only chokes are connected. The control deviation evaluation and the control time
countdown is derived from power of the smallest capacitor or of the smallest choke, whichever is less.
Any single-phase, two-phase and three-phase decompensation chokes can to be connected to any of
outputs. But in case of combined decompensation systems, it is recommended to connect capacitors
to the outputs 1.1÷1.4 in order
the CT-test (see further below) can be optionally used.
By default, the choke control is set as Off in a shipped controller or after its initialization. With this
setting the controller does not use chokes (or, generally, sections with inductive character ) that are
available - such sections are permanently disconnected. Furthermore, neither available chokes in the
automatic output recognition (AOR) process are detected.
In order the AOR process to determine values of the chokes connected and the controller to use the
chokes for power factor control,
the choke control parameter must be activated first : either mixed or
non-mixed choke control mode must be set.
4.3.1.8.1 Mixed Choke Control
Usually, one or few chokes only are installed in combined compensation systems. To reach sufficient
precision of power factor control, a suitable set of capacitors are added to the choke(s) and controller
freely combines both the chokes and the capacitors as needed to reach preset target power factor.
We will call this mode as
mixed mode.
If the mixed mode set, note that
the choke control limit power factor
parameter setting affects the
control operation too ( see below ).
If the mixed mode set, a choke is connected under the following circumstances:
• controller has disconnected all capacitive sections
•
power factor is still more capacitive (leading) than that required and also more capacitive
than the choke control limit power factor value specified ( exception: while offset control
activation, this limit is neglected )
• a choke is available at least at one output and it has such a value that after its connection
it will be possible to control the power factor to desired value using a combination of
capacitive sections, that is large undercompensation will not occur after its connection
If a number of chokes are available to the controller, the most suitable one, depending on their values,
is connected, and another one is connected if the above described situation has lasted for another five
times longer than overcompensation control time specified.
If a combination of chokes are connected and undercompensation occurs, such a number of chokes
are disconnected after the undercompensation control time has elapsed, which prevent
overcompensation.
4.3.1.8.2 Non-Mixed Choke Control
There exist some applications (such as renewable resources power plants) where continuous power
factor control in some range, usually symmetric to both sides from neutral value of 1, is required. In
such cases the same or similar sets of both capacitors and chokes are installed.
The mixed choke compensation mode is often unsuitable for such installations. Therefore, so called
non-mixed mode is implemented, that differs from the mixed one in following :
•
during one control step, the controller switches combination of chokes to reach optimal
power factor
• the controller never combines capacitors with chokes (first, it switches all of capacitors off,
then switches chokes on and vice versa)
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