Ice NP900 Series, Инструкция по применению

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Application Guide - NP900 Series 373 (504
)
A996A
3.6.1.3 E
XAMPLES OF
S
ETTING GROUP CONTROL
In this chapter are presented some of most common applications for setting group
changing requirements.
In a Petersen coil compensated network is usually used directional sensitive earth fault
protection which characteristics is wanted to be controlled in between Varmetric and
Wattmetric based into if the Petersen coil is connected when the network is compensated
or is it open when the network is unearthed.
Figure 3.6.1.3-174 Setting group control with 1 wire connection from Petersen coil status.
By monitoring the state of the Petersen coil connection the setting group control can be
applied either with 1 wire or 2 wire connection depending of the application requirements.
In case of 1 wire connection is allowed the setting group change logic can be applied as in
the figure above. Petersen coil status on controls SG1 to be active and if the coil is
disconnected SG2 is active. With this practice if the wire is broken for some reason the
setting group would always be controlled to SG2.
With 2 wires connection when the Petersen coil state is monitored in both status more
security can be achieved. In addition to the direct connection below also additional logic
can be added to the control similarly to the 1 wire control. By that way single wire loss will
not effect to the correct setting group selection.