Section 2 Analog inputs
2.1 Introduction
Analog input channels must be configured and set properly 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 properly.
Measuring and protection algorithms in the IED use primary system quantities. Setting
values are in primary quantities as well and it is important to set the data about the
connected current and voltage transformers properly.
A reference PhaseAngleRef can 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.
The availability of VT inputs depends on the ordered transformer input
module (TRM) type.
2.2 Operation principle
The direction of a current depends on the connection of the CT. The main CTs are
typically star (WYE) connected and can be connected with the Star (WYE) point to the
object or from the object. This information must be set in the IED.
The convention of the directionality is defined as follows:
• Positive value of current or power means that the quantity has the direction into
the object.
• Negative value of current or power means that the quantity has the direction out
from the object.
For directional functions the directional conventions are defined as follows (see figure
5)
1MRK505222-UUS C Section 2
Analog inputs
45
Technical reference manual
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