Protected Object
Line, transformer, etc
ForwardReverse
Definition of direction
for directional functions
Measured quantity is
positive when flowing
towards the object
e.g. P, Q, I
ReverseForward
Definition of direction
for directional functions
e.g. P, Q, I
Measured quantity is
positive when flowing
towards the object
Set parameter
CTStarPoint
Correct Setting is
"ToObject"
Set parameter
CTStarPoint
Correct Setting is
"FromObject"
IEC05000456 V1 EN
Figure 2: Internal convention of the directionality in the IED
If the settings of the primary CT is correct, that is CTStarPoint set as FromObject or
ToObject according to the plant condition, then a positive quantity always flows
towards the protected object, and a Forward direction always looks towards the
protected object.
The settings of the IED is performed in primary values. The ratios of the main CTs and
VTs are therefore basic data for the IED. The user has to set the rated secondary and
primary currents and voltages of the CTs and VTs to provide the IED with their rated
ratios.
The CT and VT ratio and the name on respective channel is done under Main menu/
Hardware/Analog modules in the Parameter Settings tool or on the HMI.
3.3 Presumptions for technical data
The technical data stated in this document are only valid under the following
circumstances:
• CT and VT ratios in the IED are set in accordance with the associated main
instrument transformers. Note that for functions which measure an analogue
signal which do not have corresponding primary quantity, the 1:1 ratio shall be set
for the used analogue inputs on the IED, For example, HZPDIF.
• Parameter IBase used by the tested function is set equal to the rated CT primary
current.
• Parameter UBase used by the tested function is set equal to the rated primary
phase-to-phase voltage.
• Parameter SBase used by the tested function is set equal to sqrt(3)* IBase* UBase
for three-phase power system.
Section 3 1MRK 502 048-UEN A
Analog inputs
46
Technical manual
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