ABB RELION 670 Series Applications Manual page 356

Section 7
Impedance protection
400kV. The outer boundary
equation 388.
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 392.
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 393, 394,
tP 1
min
EQUATION1348 V1 EN-US
d
-
In min
EQUATION1349 V1 EN-US
350
RLdOutFw obtains in this particular case its value according to
= × =
K R 0.9 137.2 123.5
L L min
389
= ×
kLdRFw RLdOutFw
390 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
391 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
395 and 396.
+ ° = °
91.5
1MRK 504 152-UEN B
(Equation 388)
tP1 and tP2
(Equation 389)
(Equation 390)
(Equation 391)
(Equation 392)
(Equation 393)
(Equation 394)
Application manual