Handbuch-KnxSmartmeter-85A-en-3.odt, 2018-10-04
Seite 23 von 69
If these group objects are linked with group addresses, then they can be easily visualized in a
time-diagram.
Measurement quantities
In this section an overview of the measurement quantities is given, which are measured by the
Smartmeter. In the following table also the data type is specified, with which the group object
can be processed in the Enertex EibPC. The definition of the sign of the power and the power
factor is shown in Figure 24.
Description of the measurement quantities:
Name
KNX Data
type (dpt.)
Data type
for Enertex
EibPC
Description
Frequency
14.033 DPT_
Value_Frequenc
y in Hz
f32 in Hz
Instantaneous frequency of grid.
The frequency is determined from the voltage of channel 1.
Voltage
9.020 DPT_
Value_Volt
in mV
f16 in mV
Instantaneous voltage as a root mean square (RMS).
Current
9.021 DPT_
Value_Curr
in mA
f16 in mA
Instantaneous current as a root mean square (RMS). The
effective value is always positive, because it has no direction.
Active Power
14.056 DPT_
Value_Power
in W
f32 in W
Instantaneous active power.
Active power is the real consumed energy per unit time. It may
be positive (during Energy consumption) or negative (during
Energy generation). Refer to Figure 24.
Reactive Power
14.056 DPT_
Value_Power
in Var
f32 in Var
Instantaneous reactive power.
Reactive power is the exchanging energy between capacitance
and inductance . It can be positive (inductive) or negative
(capacitive). See also Figure 24.
Apparent Power
14.056 DPT_
Value_Power
in VA
f32 in VA
Instantaneous apparent power.
Apparent power is the value resulting from active and reactive
power. This is always positive. With the apparent power the
utilization of resources such as cables or transformers can be
assessed.
Power Factor
14.057 DPT_
Value_Power_F
actor
without unit
f32 without
unit
Instantaneous power factor.
The power factor (cos
φ
) is the ratio of active power to apparent
power. The sign is defined in Figure 24.
Spectrum-U
DPT_Harmonics
without unit
u08 without
unit
Harmonics (0. to 50.) of the voltage . Since the recording of the
test series takes a minute, the values correspond to the
harmonics one minute ago.
When transmitting a complete spectrum, four single messages
with each 14 Bytes are transmitted. In them all the harmonics of
a voltage are coded as follows:
The first byte corresponds to an index of a harmonic; i.e. an
integer number between 0 and 50. The second byte is the
amount of the harmonic corresponding to the index from the first
byte. The following 12 bytes correspond to the amount of the
next 12 harmonics. Thus, the values of 13 harmonics are
transmitted in a 14-byte message. To exploit the range of values
of a byte in an optimal way, the values of a byte are again
encoded.
For decoding, a byte needs to be interpreted as a positive
integer x (i.e. between 0 and 255) and according to the formula
V
=
10
x
−
253
80
it has to be converted into a corresponding value V which is the
ratio of the corresponding harmonic to the fundamental.
Spectrum-I
DPT_Harmonics
without unit
Harmonics (0. to 50.) of the current. Since the recording of the
test series takes a minute, the values correspond to the
harmonics one minute ago. The coding of messages and the
values corresponds to the the spectrum-U
Enertex
®
Bayern GmbH – Ebermannstädter Straße 8 - 91301 Forchheim - Deutschland - [email protected]