ABB RELION REX640 Technical Manual page 1442

Measurement functions
8.1.3 Measurement function applications
The measurement functions are used for power system measurement, supervision
and reporting to LHMI, 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 protection and control protection relays 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 protection relay analog
measurement chain can be verified during normal service by a periodic comparison
of the measured value from the protection relay 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 to keep the communication
load to a minimum and yet measurement values are reported frequently enough.
The instantaneous measurement values of several measurement functions are
available as primary values for further use in Application Configuration. The current
values are in amperes while voltage values are in kilovolts and power values in
kilovolt-amperes, watts or volt-amperes reactive.
8.1.4 Three-phase current measurement CMMXU (ANSI IA, IB, IC)
8.1.4.1 Identification
Function description
Three-phase current measurement
1442
IEC 61850 IEC 60617
identification identification
CMMXU 3I
1MRS759142 F
ANSI/IEEE C37.2
device number
IA, IB, IC
REX640
Technical Manual