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3-26
Protection Functions
Figure 3.16 – Operation characteristic of the directional earth fault protection in Res or Cap mode
857-UM001A-EN-P – July 2009
Inverse operation time
Inverse delay means that the operation time depends on the amount
the measured current exceeds the pick-up setting. The bigger the
fault current is the faster will be the operation. Accomplished
inverse delays are available for both stages I
inverse delay types are described in "Inverse Time Operation". The
device will show a scaleable graph of the configured delay on the
local panel display.
Inverse time limitation
The maximum measured secondary residual current is 10xI
maximum measured phase current is 50xI
inverse curves with high pick-up settings. See "Inverse Time
Operation" for more information.
Setting groups
There are two settings groups available for each stage. Switching
between setting groups can be controlled by digital inputs, virtual
inputs (mimic display, communication, logic) and manually.
Figure 3.15 – Block diagram of the directional earth fault stages I
ϕ> and I
ϕ>>. The
0
0
and
0N
. This limits the scope of
N
ϕ
> and I
0
Note: Res mode can be used
with compensated networks
and Cap mode is used with
ungrounded networks.
ϕ
>>
0
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