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Technical description
2 Protection functions
2.20 Second harmonic O/C stage
If2>(51F2)
VM259.EN007
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121
2.20.
Second harmonic O/C stage I
f2
>(51F2)
This stage is mainly used to block other stages. The ratio
between the second harmonic component and the fundamental
frequency component is measured on all the phase currents.
When the ratio in any phase exceeds the setting value, the
stage gives a start signal. After a settable delay, the stage gives
a trip signal.
The start and trip signals can be used for blocking the other
stages.
The trip delay is irrelevant if only the start signal is used for
blocking.
The trip delay of the stages to be blocked must be more than 60
ms to ensure a proper blocking.
Figure 2.20-1 Block diagram of the second harmonic stage.
Setting parameters of second harmonic blocking 2.Ha(51F2):
Parameter Value
Unit
Default
Description
If2>
10…100
%
10
Setting value If2/Ifund
t_f2
0.05…300.0 s
0.05
Definite operating time
S_On
Enabled;
Disabled
-
Enabled
Start on event
S_Off
Enabled;
Disabled
-
Enabled
Start off event
T_On
Enabled;
Disabled
-
Enabled
Trip on event
T_Off
Enabled;
Disabled
-
Enabled
Trip off event