Measurement Functionality - ABB 615 series Technical Manual

Section 8
Measurement functions
8.1.2
898

Measurement functionality

The functions can be enabled or disabled with the Operation setting. The corresponding
parameter values are Enable and Disable.
Some of the measurement functions operate on two alternative measurement modes:
"DFT" and "RMS". The measurement mode is selected with the X Measurement mode
setting. Depending on the measuring function if the measurement mode cannot be
selected, the measuring mode is "DFT".
Demand value calculation
The demand values are calculated separately for each measurement function and per
phase when applicable. The available measurement modes are "Linear" and
"Logarithmic". The "Logarithmic" measurement mode is only effective for phase current
and residual current demand value calculations. The demand value calculation mode is
selected with the setting parameter Configuration/Measurements/A demand Av mode.
The time interval for all demand value calculations is selected with the setting parameter
Configuration/Measurements/Demand interval.
If the Demand interval setting is set to "15 minutes", for example, the demand values are
updated every quarter of an hour. The demand time interval is synchronized to the real-
time clock of the protection relay. When the demand time interval or calculation mode is
changed, it initializes the demand value calculation. For the very first demand value
calculation interval, the values are stated as invalid until the first refresh is available.
The "Linear" calculation mode uses the periodic sliding average calculation of the
measured signal over the demand time interval. A new demand value is obtained once in
a minute, indicating the analog signal demand over the demand time interval proceeding
the update time. The actual rolling demand values are stored in the memory until the value
is updated at the end of the next time interval.
The "Logarithmic" calculation mode uses the periodic calculation using a log10 function
over the demand time interval to replicate thermal demand ammeters. The logarithmic
demand calculates a snapshot of the analog signal every 1/15 x demand time interval.
Each measurement function has its own recorded data values. In protection relay, these are
found in Monitoring/Recorded data/Measurements. In the technical manual these are
listed in the monitored data section of each measurement function. These values are
periodically updated with the maximum and minimum demand values. The time stamps
are provided for both values.
Reset of Recorded data initializes a present demand value to the minimum and maximum
demand values.
1MAC059074-MB A
615 series ANSI
Technical Manual