Measurement Function Applications - ABB RELION REX640 Technical Manual

Section 8
Measurement functions
8.1.3
1296
The accumulated energy is calculated separately as forward active (EA_FWD_ACM),
reverse active (EA_RV_ACM), forward reactive (ER_FWD_ACM) and reverse reactive
(ER_RV_ACM). Depending on the value of the unit multiplier selected with Energy
unit Mult, the calculated power values are presented in units of kWh/kVArh or in units
of MWh/MVArh.
When the energy counter reaches its defined maximum value, the counter value is
reset and restarted from zero. Changing the value of the Energy unit Mult setting resets
the accumulated energy values to the initial values, that is, EA_FWD_ACM to Forward
Wh Initial, EA_RV_ACM to Reverse Wh Initial, ER_FWD_ACM to Forward VArh
Initial and ER_RV_ACM to Reverse VArh Initial. It is also possible to reset the
accumulated energy to initial values through a parameter or with the RSTACM input.
Sequence components
The phase-sequence components are calculated using the phase currents and phase
voltages. More information on calculating the phase-sequence components can be
found in Calculated measurements

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.
in this manual.
1MRS759142 C
REX640
Technical Manual