Specification
13
3.7.2 CT POLARITY
NOTE: Take care to ensure correct polarity of the CT primary as shown above. If in doubt,
check with the CT supplier.
Take care to ensure the correct polarity of the CTs. Incorrect CT orientation leads to negative kW
readings when the set is supplying power. Take note that paper stick-on labels on CTs that show the
orientation are often incorrectly placed on the CT (!). It is more reliable to use the labelling in the
case moulding as an indicator to orientation (if available).
To test orientation, run the generator in island mode (not in parallel with any other supply) and load
the generator to around 10% of the set rating. Ensure the DSE module shows positive kW for all
three individual phase readings.
TO GENERATOR
TO LOAD
POLARITY OF CT PRIMARY
3.7.3 CT PHASING
Take particular care that the CTs are connected to the correct phases. For instance, ensure that the
CT on phase 1 is connected to the terminal on the DSE module intended for connection to the CT for
phase 1.
Additionally ensure that the voltage sensing for phase 1 is actually connected to generator phase 1.
Incorrect connection of the phases as described above results in incorrect power factor (pf)
measurements, which in turn results in incorrect kW measurements.
One way to check for this is to make use of a single-phase load. Place the load on each phase in
turn, run the generator and ensure the kW value appears in the correct phase. For instance if the
load is connected to phase 3, ensure the kW figure appears in phase 3 display and not in the display
for phase 1 or 2.
3.7.4 CT CLASS
Ensure the correct CT type is chosen. For instance if the DSE module is providing overcurrent
protection, ensure the CT is capable of measuring the overload level you wish to protect against, and
at the accuracy level you require.
For instance, this may mean fitting a protection class CT (P10 type) to maintain high accuracy while
the CT is measuring overload currents.
Conversely, if the DSE module is using the CT for instrumentation only (current protection is disabled
or not fitted to the controller), then measurement class CTs can be used. Again, bear in mind the
accuracy you require. The DSE module is accurate to better than 1% of the full-scale current reading.
To maintain this accuracy you should fit Class 0.5 or Class 1 CTs.
You should check with your CT manufacturer for further advice on selecting your CTs
Labelled as
p1,
k
or K
Labelled as
p2,
l
or L
Summary of Contents for DSE7110 MKII
Page 34: ...Installation 34 4 2 1 DSE7110 MKII TYPICAL WIRING DIAGRAM 3 PHASE 4 WIRE ...
Page 35: ...Installation 35 4 2 2 DSE7120 MKII TYPICAL WIRING DIAGRAM 3 PHASE 4 WIRE ...
Page 36: ...Installation 36 4 3 ALTERNATE TOPOLOGY WIRING DIAGRAMS 4 3 1 GENERATOR ...
Page 37: ...Installation 37 4 3 2 MAINS DSE7120 MKII ONLY ...
