ABB REL650 Applications Manual page 169

1MRK 506 334-UUS A
Application manual
• K = 0.9 for lines longer than 100 miles
L
• K = 0.85 for lines between 50 and 100 miles
L
• K = 0.8 for lines shorter than 50 miles
L
Multiply the required resistance for the same safety factor K
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 81.
= ×
RLdOutFw K R
L L
EQUATION1343 V1 EN
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
maximum possible value of RLdInFw.
RLdInFw = kLdRFw·RLdOutFw = 98.8
EQUATION1344 V2 EN
The load angles, which correspond to external δ
oscillation detection characteristic in forward direction, are calculated with sufficient
accuracy according to equation
æ
Z
d
= × ç
2 arc tan
ç
Out
×
2 RLdOutFw
è
EQUATION1345 V1 EN
æ
Z
d
= × ç
2 arc tan
ç
In ×
2 RLdInFw
è
EQUATION1346 V1 EN
The required setting tP1 of the initial oscillation detection timer depends on the load angle
difference according to equation 85.
= × =
0.9 137.2 123.5
min
W
Out
83 and 84 respectively.
ö
æ
155.75
S
÷ = ×
2 arc tan
ç
÷
×
è 2 123.5
ø
ö
æ
155.75
S
÷ = ×
2 arc tan
ç
÷
è 2 98.8
ø
max
Impedance protection
with the ratio between actual
L
W
82 presents the corresponding
and internal δ boundary of proposed
In
ö
= °
64.5
÷
ø
ö
= °
76.5
÷
×
ø
Section 6
(Equation 81)
(Equation 82)
(Equation 83)
(Equation 84)
163