6.9.1.4. Primary and Secondary data for CT and CT/VT meters
Meters installed behind measurement transformers with Current Transformer (CT) on Low Voltage (LV) network
or with Current and Voltage Transformers (CT/VT) on High Voltage (HV) network can provide the metered data
either as:
- Secondary values, i.e. the values actually seen by the meter
- Primary values, i.e. the values at the primary of the measurement transformers (CT or CT/VT)
To that effect the Transformer ratios for CT and VT can be programmed into the meter.
Programming the Tansformer ratio at a value of unity will result in the meter providing all data as secondary
values.
Logging of CT VT reprogramming (and TER scaler / unit)
The meter keeps a history table (FIFO) of the last 10 modifications of specific installation parameters:
- Current and voltage transformers ratios
- Total active energy registers scaler/unit
These event loggers cannot be deleted.
Both event loggers are available for remote or local reading through the meter communication ports.
Note for MID meters: The current parameters values and the event logger entries are always available to the
end customer on the meter display in the MID sequence. The event loggers cannot be deleted.
In addition, when the event logger is full (10 elements), a new programming is allowed only if the oldest entry is
older than 90 days; otherwise the reprogramming action is rejected.
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