Handbuch-KnxSmartmeter-85A-en-3.odt, 2018-10-04
Seite 26 von 69
Bidirectional Counter
The device can be used as a bidirectional counter and as a balancing counter at the same time.
Bidirectional counter are always required when at the measurement point of the counter an
energy flow occurs in both directions and in addition the energy flow in one direction is different
billed as the energy flow in the opposite direction. This is the case e.g. during the operation of a
PV-system in a residential building. If the Smartmeter is installed at the house connection line
then the registers for both directions must be used.
For this purpose each energy counter of the Smartmeter (i.e. active energy counter-channel 1,
active energy counter-channel 2, active energy counter-channel 3 and active energy counter
three-phase) has three registers. One register for the consumption (group object “Active energy
counter (consumption)”), one register for the generation (group object “Active energy counter
(generation)”) and one register for the balance (group object “ Active energy counter (balance)”).
The register for the consumption only counts, when an energy flow occurs in positive power flow
direction. The register for the generation only counts, when an energy flow occurs in negative
power flow direction. The register for the balance counts in both cases.
The power arrow direction is determined by the orientation of the current sensors. The power
arrow which is glued on the current sensors
P+
indicates the positive power arrow direction.
Typically the current sensors are mounted so that the power arrow is oriented from the energy
source to the energy consumer load. This means that in the example of the installation of the
counter at the connection line of the residential home the current sensors are oriented so, that
the power arrow shows from the national grid to the consumer loads in the residential home. If
energy is currently consumed in the house, then the consumption counter counts in that case. If
in the house energy is never generated, the generation counter is always zero. If in the house
energy can be generated, e.g. by a PV-facility, then different scenarios are possible:
Scenario
Consumer
counter
Generation
counter
Consequence
More energy is consumed
than generated in the house.
counting
not counting
Energy is charged by the supply rate of
the energy provider.
More energy is generated
than consumed in the house.
not counting
counting
Energy is charged by the feed-in tariff
of the energy provider.
As much as energy is
consumed as generated in the
house.
not counting
not counting
Nothing is charged.
The “Active energy counter (balance)” also counts in the first both scenarios. For the charge of
the energy delivery only the value of the “Active energy counter (consumption)” is used.
However,for the charge of the compensation only the value of the “Active energy counter
(generation)” is used.
The “Active energy counter (generation)” is by definition always negative, since it is a negative
energy flow related to the power count arrow. With this definition it is always :
Active energy counter (balance) = Active energy counter (consumption) + Active energy counter
(generation)
Just as the energy counters each tariff costs counter has three registers for consumption,
generation and balance. They are treated in the same way, i.e. during an energy consumption
the tariff cost counter counts in the group object “Tariff costs counter (consumption)”, during an
energy generation the tariff cost counter counts in the group object “ Tariff costs counter
(generation)” and the tariff cost counter in the group object “ Tariff costs counter (balance)”
always counts.
Thus with regard to the costs separate registers are also used for each count direction. To count
a compensation directly in a cost counter, the feed-in tariff in tariff 1 can be specified. In the
group object "Tariff costs counter (generation)” for tariff 1 one can directly read the accumulated
compensation. In order that the compensation in the counter appears positive, a negative rate
(=compensation) has to be specified in the panel for the rate of tariff 1. If also energy delivery
costs are to be counted , the delivery rate of the supplier of electric energy can be indicated in
tariff 2. In the group object "Tariff costs counter (consumption)" for tariff 2 the accumulated
current costs can be read directly. The group object "Tariff costs counter (consumption)" for tariff
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