ABB RELION 670 Series Applications Manual page 375

1MRK 505 343-UEN B
400kV. The outer boundary
equation 432.
RLdOutFw
EQUATION1343 V1 EN-US
It is a general recommendation to set the inner boundary
characteristic to 80% or less of its outer boundary. Exceptions are always possible, but must
be considered with special care especially when it comes to settings of timers
included in oscillation detection logic. This requires the maximum permitted setting values of
kLdRFw = 0.8. Equation
factor
RLdInFw .
RLdInFw
EQUATION1344 V3 EN-US
The load angles, which correspond to external δ
oscillation detection characteristic in forward direction, are calculated with sufficient accuracy
according to equation
d
= ×
2 arc tan
Out
EQUATION1345 V1 EN-US
d
= ×
2 arc tan
In
EQUATION1346 V1 EN-US
The required setting
difference according to equation 436.
d
=
tP 1
EQUATION1347 V1 EN-US
The general tendency should be to set the
possible to further increase the external load angle δ
boundary of the oscillation detection characteristic. The minimum required value is calculated
according to the procedure listed in equation 437, 438,
tP 1
min
EQUATION1348 V1 EN-US
d
-
In min
EQUATION1349 V1 EN-US
Application manual
RLdOutFw obtains in this particular case its value according to
= × =
K R 0.9 137.2 123.5
L L min
433
= ×
kLdRFw RLdOutFw
434 and
æ
Z
S
ç
ç
×
2 RLdOutFw
è
æ
Z
S
ç
ç
×
2 RLdInFw
è
max
tP1 of the initial oscillation detection timer depends on the load angle
d
- ° -
76.5 64.5
=
In Out
× ° ×
f 360 2.5 360
si
=
30 ms
d
= ° × × +
360 f tP 1
si min
× = W
presents the corresponding maximum possible value of
= W
98.8
and internal δ
Out
435 respectively.
ö
æ ö
155.75
÷ = ×
2 arc tan
ç ÷
÷
×
è 2 123.5 ø
ø
ö
æ ö
155.75
÷ = ×
2 arc tan
ç ÷
÷
×
è 2 98.8 ø
ø
°
=
13.3 ms
°
tP1 time to at least 30 ms, if possible. Since it is not
Out
= ° × ×
360 2.5 0.030 64.5
Out
RLdInFw of the oscillation detection
boundary of proposed
In
= °
64.5
= °
76.5
, it is necessary to reduce the inner
439 and 440.
+ ° = °
91.5
Section 7
Impedance protection
(Equation 432)
tP1 and tP2
(Equation 433)
(Equation 434)
(Equation 435)
(Equation 436)
(Equation 437)
(Equation 438)
369