4.81
Date Code 20170814
Instruction Manual
SEL-700G Relay
Protection and Logic Functions
Group Settings (SET Command)
Figure 4.48
Single-Blinder Typical Settings
Double-Blinder Scheme
The double-blinder scheme, shown in Figure 4.49, consists of mho element
78Z1 and two blinder pairs: outer resistance blinder 78R1 and inner resistance
blinder 78R2. This scheme uses timer 78D as part of its logic to detect out-of-
step conditions. The scheme declares an out-of-step condition if the positive-
sequence impedance stays between the two blinders for more than 78D
seconds and advances farther inside the inner blinder. The logic issues an out-
of-step trip once an out-of-step condition is established and the positive-
sequence impedance exits the mho circle.
Figure 4.49
Double-Blinder Scheme Operating Characteristics
N
B
X’
d
Summary of Contents for SEL-700G Series
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