What should you watch out for when manually entering energy meter values in SIMATIC powerrate?
As well as automatically capturing energy values the PRE_SUM / PR3_SUM capture blocks also support the manual input of energy meter values in the WinCC user interface. Please note the following points.
- Capture mode of the PRE_SUM / PR3_SUM blocks
- Weighting factor for scaling the input values
- Handling of units other than kilowatt hours (kWh)
- Parameter "INP_SEL = 1" with Integer Counter
- Parameter "INP_SEL = 2" with Analog Counter
You cannot enable manual input of values in the "Pulse" and "Calculation" capture modes.
Weighting factor for scaling the input value
Just as in automatic operating mode, in the "Manual" mode the "WEIGHT_A" weighting factor set at the call interface of the PRE_SUM / PR3_SUM block is also taken into account for scaling the input value. By default, the system expects input in the input mask in WinCC Runtime of values in the unit "kWh" (see figure below of the "Input"/"Edit" view).
For this you set the weighting factor "WEIGHT_A" to the value "1" (1,000e+000) on the PRE_SUM/PR3_SUM block. With this setting the values you enter in the input mask are interpreted as "kWh".
- The user must convert the values read into "kWh" before entering them in the input mask.
- The WEIGHT_A scaling factor on the PRE_SUM / PR3_SUM block is changed accordingly.
- Wh: Factor: 0.001 (WEIGHT_A := 1,000e-003)
- MWh: Factor: 1000 (WEIGHT_A := 1,000e-003)
In this case you must also change the faceplate of the input mask to the new unit scaling.
A description of this is given in the SIMATIC powerrate manual at this link. (You must change the four parameters V_MAN, V_MAN_L1, …_L2, …_L3 to the required unit scaling - Wh or MWh, for example.)
A special case is the temporary switching from "Auto" to "Manual" during runtime (when there is a brief interruption of the field bus connection, for example). In this case the values read and the WEIGHT_A set on the PRE_SUM / PR3_SUM block must be converted before being entered in the input mask.
The measuring instrument delivers the energy meter value via the field bus connection on the basis of "Wh". However, on the display the energy meter is shown with the "kWh" unit.
Thus, before entering the meter value you must convert it to the expected unit of "Wh".
(For example, read value: "734676.67 kWh" > Input: "734676670 Wh").
For this case the display of the default unit "kWh" in "Input"/"Edit" view does not apply. Ignore the unit for the duration of the temporary manual operating mode.
This scenario of temporary manual input is not usual in practice because the automatic capturing cycle (15 minutes, for example) generally cannot be realized by manual capturing.