ABB REG650 Technical Manual page 384

Section 13
Monitoring
378
Default value for parameter k is 0.00. With this value the new calculated value is
immediately given out without any filtering (that is, without any additional delay).
When k is set to value bigger than 0, the filtering is enabled. Appropriate value of k
shall be determined separately for every application. Some typical value for k =0.14.
Zero point clamping
In order to avoid erroneous measurements when either current or voltage signal is
not present, the amplitude level for current and voltage measurement is forced to
zero. When either current or voltage measurement is forced to zero automatically
the measured values for power (P, Q & S) and power factor are forced to zero as
well. Since the measurement supervision functionality, included in the CVMMXN
function, is using these values the zero clamping will influence the subsequent
supervision (observe the possibility to do zero point clamping within measurement
supervision, see section
Compensation facility
In order to compensate for small amplitude and angular errors in the complete
measurement chain (CT error, VT error, IED input transformer errors and so on.) it
is possible to perform on site calibration of the power measurement. This is
achieved by setting the complex constant which is then internally used within the
function to multiply the calculated complex apparent power S. This constant is set
as amplitude (setting parameter PowAmpFact, default value 1.000) and angle
(setting parameter PowAngComp, default value 0.0 degrees). Default values for
these two parameters are done in such way that they do not influence internally
calculated value (complex constant has default value 1). In this way calibration, for
specific operating range (for example, around rated power) can be done at site.
However, to perform this calibration it is necessary to have an external power
meter with high accuracy class available.
Directionality
CTStartPoint defines if the CTs earthing point is located towards or from the
protected object under observation. If everything is properly set power is always
measured towards protection object.
"Measurement supervision").
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Technical Manual