4.30Grid meter

The Grid Meter is the service behind the Grid Meter panel. It reads the electricity meter at your supply point, either a KNX meter on group addresses or a Modbus meter, and publishes every reading as a System Value that the panel, and any object that can use a System Value, can show.

#What it does

• Reads voltage, current, frequency, active power, power factor and the consumed and generated energy of one meter.
• Publishes each reading as a System Value named grid: followed by the field, for example grid:activePower.
• Works out two extra values from the active power: import power (power taken from the grid) and export power (power sent to the grid), both in kW.
• Reads only active energy (consumed and generated). Apparent and reactive values are not offered.

It needs gateway runtime 1.0.14 or later.

#Before you enable it

• A KNX meter must send its values on group addresses and the KNX engine must be working.
• A Modbus meter must first be added as a device under the RS485 interface, the RS232 interface or Modbus TCP, so that its datapoints exist. See Modbus devices and datapoints.

#Settings

Open Server > Internal services > Grid Meter. Enabled is Off by default.

#The values

The formats on offer are 2-byte float (DPT 9), 4-byte float (DPT 14), 4-byte signed counter (DPT 13) and 4-byte unsigned counter (DPT 12). The defaults follow the usual KNX meter layout, so change one only if your meter's ETS table lists a different data type. A KNX meter that sends power in W defaults to a 4-byte float.

The five energy periods follow the usual register layout of KNX energy meters: the running total, a daily register and a monthly register, each with its own previous-period value.

#How it works on the gateway

• KNX: the gateway watches every mapped group address, asks the meter for the current value after a deploy or when the KNX connection comes back, and decodes each value by its format.
• Modbus: the gateway copies each mapped datapoint's value as it is read. The datapoint's own scale and unit already give volts, amps, kW and kWh, so no format is chosen.
• Sign of the power: the meter's Active power is positive for consumption and negative for generation. Import power is the positive part, and export power is the negative part shown as a positive number. Only one of the two is above zero at a time.
• Values for other objects: the readings are published as System Values grid:voltageL1, grid:currentL1, grid:frequency, grid:activePower, grid:powerFactor, grid:consumedTotal, grid:generatedTotal, grid:consumedDay, and so on, plus grid:importPowerKw and grid:exportPowerKw.

#Example

A three-phase KNX meter that sends power in kW.

1. Open Server > Internal services > Grid Meter. Turn Enabled on, set Meter Type KNX meter, Power Unit kW and Phase Type Three-phase meter.
2. Under Group Addresses, enter the address the meter sends each value on, for example Voltage L1 0/4/48, Active power 0/4/60 and Consumed energy - total 0/4/70.
3. Check Value formats against the meter's ETS table.
4. Add a Grid Meter object to a page, then deploy.

#Tips and common problems

• Every value shows --: the service is not enabled, the project was not deployed, or no address is mapped. For a KNX meter check that the meter answers read requests, because the gateway reads the values once after a deploy.
• The power is 1000 times too large or small: Power Unit does not match what the meter reports. Choose W for a meter that sends watts.
• Import and export are swapped: the meter reports consumption as a negative number. Many meters have a parameter for the direction; change it in ETS.
• Energy values look wrong: check the value format. A counter read as a float gives nonsense numbers.
• The L2 and L3 values are missing: set Phase Type to Three-phase meter.

#See also

• Grid Meter panel
• KNX engine
• Modbus devices and datapoints
• Power Flow Manager