NOVAR 300 Operation & Maintenance Manual
NOVAR_CM
Page 20 of 29
3.6 CONNECTION ERRORS
NOVAR 300 gives a certain amount of information to assist with connection. There are six
possible ways in which it is possible to connect a system. Of these six, only one is correct.
For three of the others, NOVAR 300 will give indication of a connection error as follows.
At system unity power factor, the NOVAR 300 error mode is looking for a phase angle of
90
°
between amps and volts. As a system can in theory be operating anywhere within a
band of 90
°
either side of this, the error mode looks for its inputs to be within this band.
Refer to Figure 4 for vector diagrams showing the correct and incorrect connections.
The correct connection (a)
Input is I
A
with V
BC
.
For this case, the NOVAR will go straight into AUTO mode.
The most common connection error is that of a reversed CT (b). In this case the NOVAR
will display 270
°
for a system at unity power factor.
If V
BA
is selected instead of V
BC
(c) then the NOVAR will display 150
°
.
If V
CA
is selected instead of V
BC
(d) then the NOVAR will display 210
°
.
The above values will change if the system is not at unity power factor (e.g. if the system is
at 40
°
lagging then a CT reversal would appear as 230°).
Because V
AB
or V
AC
are within the above stated bands, then the NOVAR is not able to
distinguish between these and a system working at the relevant power factor.
If V
AB
is selected (e) then the NOVAR will display a cos
ϕ
of 0.5 leading corresponding to an
angle of 60
°
leading.
If V
AC
is selected (f) then the NOVAR will display a cos
ϕ
of 0.5 lagging corresponding to an
angle of 60
°
lagging.
3.7 USE OF EXPANDED DISPLAY
Once it is known that the NOVAR is connected into the system correctly, it is necessary to
set up the working parameters of the unit.
If a display model is being used, then it enables more accurate settings if expanded display
mode is now entered. This is achieved by pressing the lower push button for more than 5
seconds.
