The relay calculates the scaling factors based on the set VT primary, and secondary voltage values.
The relay measures secondary voltages, which are the voltage outputs from the VT installed into the
application's primary circuit. The rated primary and secondary voltages of the VT need to be set for the
relay to "know" the primary and per-unit values. In modern protection devices this scaling calculation is
done internally after the voltage transformer's primary and secondary voltages are set.
Normally, the primary line-to-line voltage rating for VTs is 400 V...60 kV, while the secondary voltage
ratings are 100 V...210 V. Non-standard ratings can also be directly connected as the scaling settings
are flexible and have large ranges.
Example of VT scaling
The following figure presents how VTs are connected to the relay's measurement inputs. It also shows
the VT ratings. In the figure below, two line-to-line voltages are connected along with the zero
sequence voltage; therefore, the 2LN+U0 mode must be selected. Other possible connections are
presented later in this chapter.
Figure. 5.2.2 - 66. Connections.
The following table presents the initial data of the connection.
Table. 5.2.2 - 24. Initial data.
PPha
hase v
se volta
oltage V
ge VTT
- VT primary: 20 000 V
- VT secondary: 100 V
ZZer
ero sequence v
o sequence volta
oltage V
ge VTT
- U4 VT primary: 20 000 V
- U4 VT secondary: 100 V
- the zero sequence voltage is connected similarly to line-to-line voltages (+U0).
- in case wiring is incorrect, all polarities can be individually switched by 180 degrees in the relay.
The protection can be based on line-to-line voltages or on line-to-earth voltages. This selection is
defined in the "Measured magnitude" of each protection stage menu separately (
Protection
→
Voltage
→
[protection stage menu]
→
INFO; see the image below).
A
AQ
Q-C213
-C213
Instruction manual
Version: 2.04
67
Содержание AQ-C213
Страница 1: ...AQ C213 Capacitor bank protection IED Instruction manual ...
Страница 308: ...Figure 7 4 184 Example block scheme A AQ Q C213 C213 Instruction manual Version 2 04 307 ...
Страница 330: ...Figure 8 14 207 Panel cutout dimensions and device spacing A AQ Q C213 C213 Instruction manual Version 2 04 329 ...