Multiply the required resistance for the same safety factor K
L
with the ratio
between actual voltage and 400kV when the rated voltage of the line under
consideration is higher than 400kV. The outer boundary
RLdOutFw
obtains in this
particular case its value according to equation
.
min
0.9 137.2 123.5
L
L
RLdOutFw K
R
=
×
=
×
=
W
EQUATION1343 V1 EN-US
(Equation 82)
It is a general recommendation to set the inner boundary
RLdInFw
of the
oscillation detection characteristic to 80% or less of its outer boundary. Take
special care during the settings of timers
tP1
and
tP2
which is included in the
oscillation detection logic. This requires the maximum permitted setting values of
factor
kLdRFw
= 0.8. Equation
presents the corresponding maximum possible
value of
RLdInFw
.
98.8
=
×
=
W
RLdInFw
kLdRFw RLdOutFw
EQUATION1344 V3 EN-US
(Equation 83)
The load angles, which correspond to external δ
Out
and internal δ
In
boundary of
proposed oscillation detection characteristic in forward direction, are calculated
with sufficient accuracy according to equation
155.75
2 arc tan
2 arc tan
64.5
2
2 123.5
d
æ
ö
æ
ö
ç
÷
= ×
= ×
=
°
ç
÷
ç
÷
×
×
è
ø
è
ø
S
Out
Z
RLdOutFw
EQUATION1345 V1 EN-US
(Equation 84)
max
155.75
2 arc tan
2 arc tan
76.5
2
2 98.8
d
æ
ö
æ
ö
ç
÷
= ×
= ×
=
°
ç
÷
ç
÷
×
×
è
ø
è
ø
S
In
Z
RLdInFw
EQUATION1346 V1 EN-US
(Equation 85)
The required setting
tP1
of the initial oscillation detection timer depends on the
load angle difference according to equation
76.5
64.5
1
13.3
360
2.5 360
In
Out
si
tP
ms
f
d
d
-
° -
°
=
=
=
×
°
×
°
EQUATION1347 V1 EN-US
(Equation 86)
The general tendency should be to set the
tP1
time to at least 30 ms, if possible.
Since it is not possible to further increase the external load angle δ
Out
, it is
necessary to reduce the inner boundary of the oscillation detection characteristic.
The minimum required value is calculated according to the procedure listed in
equation
,
Section 7
1MRK 505 393-UEN B
Impedance protection
140
Line differential protection RED650 2.2 IEC
Application manual
Summary of Contents for RED650
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