Instruction manual
–
AQ G3x7 Generator protection IED
22 (211
)
3.1.4
L
INE MEASUREMENT
The input values of the AQ300 devices are the secondary signals of the voltage
transformers and those of the current transformers.
These signals are pre-
processed by the “Voltage transformer input” functi
on block and by
the “Current transformer input” function block. The pre
-processed values include the Fourier
basic harmonic phasors of the voltages and currents and the true RMS values. Additionally,
it is in these function blocks that parameters are set concerning the voltage ratio of the
primary voltage transformers and current ratio of the current transformers.
Based on the pre-
processed values and the measured transformer parameters, the “Line
measurement” function block calculates
- depending on the hardware and software
configuration - the primary RMS values of the voltages and currents and some additional
values such as active and reactive power, symmetrical components of voltages and
currents. These values are available as primary quantities and they can be displayed on the
on-line screen of the device or on the remote user interface of the computers connected to
the communication network and they are available for the SCADA system using the
configured communication system.
3.1.4.1
Reporting the measured values and the changes
It is usual for the SCADA systems that they sample the measured and calculated values in
regular time periods and additionally they receive the changed values as reports at the
moment when any significant change is detected in the primar
y system. The “Line
measurement” function block is able to perform such reporting for the SCADA sy
stem.
3.1.4.2
Operation of the line measurement function block
The inputs of the line measurement function are
•
the Fourier components and true RMS values of the measured voltages and
currents
•
frequency measurement
•
parameters.
The outputs of the line measurement function are
•
displayed measured values
•
reports to the SCADA system.