Measurement Function Applications; Three-Phase Current Measurement Cmmxu - ABB RELION SMU615 Technical Manual

Measurement functions
7.1.3

Measurement function applications

The measurement functions are used for power system measurement, supervision
and reporting to a monitoring tool within PCM600, or to the station level, for
example, with IEC 61850. The possibility to continuously monitor the measured
values of active power, reactive power, currents, voltages, power factors and so on,
is vital for efficient production, transmission, and distribution of electrical energy.
It provides a fast and easy overview of the present status of the power system to
the system operator. Additionally, it can be used during testing and commissioning
of merging units to verify the proper operation and connection of instrument
transformers, that is, the current transformers (CTs) and voltage transformers
(VTs). The proper operation of the merging unit analog measurement chain can
be verified during normal service by a periodic comparison of the measured value
from the merging unit to other independent meters.
When the zero signal is measured, the noise in the input signal can still produce
small measurement values. The zero point clamping function can be used to ignore
the noise in the input signal and, hence, prevent the noise to be shown in the user
display. The zero clamping is done for the measured analog signals and angle values.
The demand values are used to neglect sudden changes in the measured analog
signals when monitoring long time values for the input signal. The demand values
are linear average values of the measured signal over a settable demand interval.
The demand values are calculated for the measured analog three-phase current
signals.
The limit supervision indicates, if the measured signal exceeds or goes below the
set limits. Depending on the measured signal type, up to two high limits and up to
two low limits can be set for the limit supervision.
The deadband supervision reports a new measurement value if the input signal
has gone out of the deadband state. The deadband supervision can be used in
value reporting between the measurement point and operation control. When the
deadband supervision is properly configured, it helps in keeping the communication
load in minimum and yet measurement values are reported frequently enough.
7.1.4

Three-phase current measurement CMMXU

7.1.4.1 Identification
Function description
Three-phase current measure-
ment
190
IEC 61850 IEC 60617
identification identification
CMMXU 3I
1MRS758407 C
ANSI/IEEE
C37.2 device
number
3I
SMU615
Technical Manual