ABB Relion 670 series - Page 447

• K
L
= 0.9 for lines longer than 100 miles
• K
L
= 0.85 for lines between 50 and 100 miles
• K
L
= 0.8 for lines shorter than 50 miles
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 (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. Exceptions are always
possible, but must be considered with special care especially when it comes to settings of
timers tP1 and tP2 included in 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 (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
(Equation 410)
max
155.75
2 arctan 2 arctan 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 (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 (Equation 412)
1MRK 506 369-UUS - Section 8
Impedance protection
Line distance protection REL670 2.2 ANSI 441
Application manual