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Percentage restraint characteristics
The percentage restraint characteristic is tested on the outflow current (I out ) and infeed current
(I in ) plane as shown in Figure 6.5.1.3 by applying an infeed current to one relay and an outflow
current to another relay.
I out
DIFI2
DIFI1
DIFI1, DIFI2: Setting value
Figure 6.5.1.3 Percentage Restraining Characteristic on I in -I out Plane
Characteristic A is expressed by the following equation,
I out ≤ (5/7) (I in - DIFI1)
Characteristic B is expressed by the following equation,
I out ≤ DIFI2
where, DIFI1 and DIFI2 are setting values.
• Select the "Logic circuit" on the "Test" sub-menu screen to display the "Logic circuit" screen.
• Enter a signal number 48 to observe the DIF-A output at monitoring jack A and press the
ENTER key.
• Apply a fixed infeed current to one relay. Apply an outflow current to another relay, change the
magnitude of the current applied and measure the value at which the element operates.
• Repeat the above by changing the magnitude of the infeed current.
• Check that the measured value of the outflow current is within ± 7% of the theoretical values
obtained using the equations mentioned above. (The infeed current is more than 0.5 × In).
I in = I out
B
A
DIFI1 + 7/5 DIFI2
⎯
⎯
135
6 F 2 S 0 8 2 8
I in
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