Introduction - ABB REC650 Applications Manual

1MRK 511 286-UUS A
Section 4
4.1
4.2
4.2.1
Application manual
Analog inputs

Introduction

Analog input channels in the IED must be set properly in order to get correct measurement
results and correct protection operations. For power measuring and all directional and
differential functions the directions of the input currents must be defined in order to reflect
the way the current transformers are installed/connected in the field ( primary and
secondary connections ). Measuring and protection algorithms in the IED use primary
system quantities. Consequently the setting values are expressed in primary quantities as
well and therefore it is important to set the transformation ratio of the connected current
and voltage transformers properly.
The availability of CT and VT inputs, as well as setting parameters depends on the ordered
IED.
A reference PhaseAngleRef must be defined to facilitate service values reading. This
analog channels phase angle will always be fixed to zero degrees and all other angle
information will be shown in relation to this analog input. During testing and
commissioning of the IED the reference channel can be changed to facilitate testing and
service values reading.
Setting guidelines
Setting of the phase reference channel
All phase angles are calculated in relation to a defined reference. An appropriate analog
input channel is selected and used as phase reference. The parameter PhaseAngleRef
defines the analog channel that is used as phase angle reference.
The initially connected phase-to-earth voltage is usually chosen as PhaseAngleRef. A
phase-to-phase voltage can also be used in theory, but a 30 degree phase shift between the
current and voltage is observed in this case.
If no suitable voltage is available, the initially connected current channel can be used.
Although the phase angle difference between the different phases will be firm, the whole
system will appear to rotate when observing the measurement functions.
Section 4
Analog inputs
61