NOVAR 300 Operation & Maintenance Manual NOVAR_CM
Page 23 of 29
4.1.6
Input magnitude errors and transients
So long as both voltage and current inputs remain within the converter range specified in
section 4.0, the NOVAR will continue to operate, even if rms values lie outside of the ranges
specified in section 2 (excluding low voltage reset). However, if either the voltage or current
input exceeds the converter limits specified in section 1.1, the NOVAR will be disabled from
performing any further capacitor changes. This situation will occur for example very high or
peaky voltage or currents, or for any interference which the NOVAR is not able to filter out
by other means. When the inputs return to within their permitted limits, the NOVAR will
continue to function as normal.
4.1.7 Internal NOVAR hardware fault
The IND and CAP LEDs will flash alternately and the alarm relay (if fitted) will toggle on and
off. This is a very slow toggle, the on time for each LED being about two seconds.
4.1.8 Perceived software fault
The intelligence of the NOVAR 300 range of controllers is based around a highly integrated
micro-controller. This system includes a software watchdog - a piece of hardware built into
the processor to ensure that it cannot operate in any way which is not allowed. This system
will reset the micro-controller, and therefore the NOVAR, if it is not regularly informed that all
is well.
The NOVAR indicates that this is the case by either displaying CAL on its display or by
alternating between this and its sign-on display whilst flashing the IND LED briefly.
NB This is not an indication of a software error in the NOVAR - it is impossible for a NOVAR
to be despatched unless its software is correct. If either of these situations does occur,
there will be some cause not caught by the above specific error traps (e.g. voltage < 50 %)
If either of these situations occur, please contact our applications department for further
advice.
4.1.9 Capacitors permanently connected
If the CAP light continues to flash after the automatically controlled capacitors are 'switched
out', check for capacitors which have been permanently connected.
4.1.10 Hunting
This symptom must not be confused with switching caused by rapid fluctuations of the load.
If the control scale settings are too close, a point in the load level may be reached where
the introduction of another capacitor will make the total load LEAD marginally more than the
CAP setting. The capacitor will then be disconnected after the selected relay operation time,
causing the total load to LAG more than the IND setting. If the factory load remains steady,
the sequence will be repeated after the selected safety lockout time. The regularity of
switching is an indication of hunting. This can be rectified by increasing the control scale
settings marginally.
On systems liable to high voltages, it may be necessary to set the control scales at higher
settings than would otherwise be required at the nominal voltage. This is because the kvar
rating of the capacitors is proportional to the square of the line voltage.
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