CCS WattNode Pulse WNB-3D-240-P, Reference Manual

Page: 28 / 38

28 Operating Instructions
Using the “Pulses Per kilowatt-hour” PpKWH value from the table above for your model and
current transformer, you can compute energy and power as follows (multiply by 1000 to convert
kilowatts to watts):
Energy (kilowatt-hours) = PulseCount / PpKWH
Power (kilowatts) = 3600
•
PulseFreq / PpKWH
Power and Energy Equations
This section shows how to compute power and energy from pulses for any full-scale pulse output
frequency. The power is proportional to the pulse frequency, while the energy is proportional to
the count of pulses.
For these calculations, we use the following variables:
●
NVac
- This is the
nominal
line voltage (phase to neutral) of the WattNode model. For delta
model, this is a virtual voltage, since there may not be a neutral connection. Note: this is
not
the actual measured voltage.
●
PpPO - “Phases per Pulse Output”. This is the number of meter voltage phases associ-
ated with a pulse output channel. This may be different than the number of phases you are
monitoring.
○
Standard
and
Option DPO
(Dual Positive Outputs):
PpPO
= 3
○
Option P3 (Per-Phase Outputs): PpPO = 1
○
Option PV
(Photovoltaic):
PpPO
= 2 for outputs
P1
and
P2
,
PpPO
= 1 for output
P3
●
CtAmps - This is the current transformer (CT) rated amps. Note: If the conductors being
measured are passed through the CTs more than once, then CtAmps is the rated CT current
divided by the number of times that the conductor passes through the CT.
●
FSHz
- This is the full-scale pulse frequency of the meter. It is 4.00 Hz, unless the meter was
ordered with
Option Hz=xxx
(where
xxx
specifies the full-scale pulse frequency) or
Option
Kh
.
●
PulseCount - This is the measured pulse count, used to compute energy. You can use the
count of pulses over specified periods of time (such as a month) to measure the energy for
that period of time.
●
PulseFreq
- This is the measured pulse frequency from one of the pulse channels (
P1
,
P2
,
or
P3
). This can be computed by counting the number of pulses in a fixed period of time and
then dividing by the number of seconds in that time period. For example, if you count 720
pulses in five minutes (300 seconds), then
PulseFreq
= 720 / 300 = 2.40 Hz.
The values of the constant parameters are in the following table.
WattNode Models NVac Standard FSHz Values
WNB-3Y-208-P 120 4.00 Hz
WNB-3Y-400-P 230 4.00 Hz
WNB-3Y-480-P 277 4.00 Hz
WNB-3Y-600-P 347 4.00 Hz
WNB-3D-240-P 120* 4.00 Hz
WNB-3D-400-P 230* 4.00 Hz
WNB-3D-480-P 277* 4.00 Hz
*Note: these are “virtual” line-to-neutral voltages used for delta model power
and energy computations.
Table 7: Power and Energy Parameters