ABB REL670 2.2 IEC - Page 419

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 408.
min
0.9 137.2 123.5
L L
RLdOutFw K R= × = × = W
EQUATION1343 V1 EN-US (Equation 408)
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 409 presents the corresponding maximum possible
value of RLdInFw.
98.8= × = WRLdInFw kLdRFw RLdOutFw
EQUATION1344 V3 EN-US (Equation 409)
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 410 and 411 respectively.
155.75
2 arctan 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 410)
max
155.75
2 arctan 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 411)
The required setting tP1 of the initial oscillation detection timer depends on the
load angle difference according to equation
412.
76.5 64.5
1 13.3
360 2.5 360
In Out
si
tP ms
f
d d -
° - °
= = =
× ° × °
EQUATION1347 V1 EN-US (Equation 412)
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
413, 414, 415 and 416.
1MRK 506 369-UEN B Section 8
Impedance protection
Line distance protection REL670 2.2 IEC 413
Application manual