sepam 20 user manual - Schneider Electric

3
MT10426
MT10865
MT10866
Protection functions Phase undercurrent
ANSI code 37
Operation Block diagram
This protection is single-phase:
b it picks up when phase 1 current drops below the Is
set point
b it is inactive when the current is less than 10 % of Ib
b it is insensitive to current drops (breaking) due to
circuit breaker tripping
b it includes a definite time delay T.
3/8
DE50367
Characteristics
Is set point
Setting 15 % Ib y Is y 100 % Ib by steps of 1 %
Accuracy (1) Pick-up/drop-out ratio
T time delay
±5 %
106 % ±5 % for Is > 0.1 In
Setting
Accuracy
50 ms y T y 300 s
(1) t
T
0 0,1 Ib Is I
±2 % or ±25 ms
Resolution 10 ms or 1 digit
Operating principle Characteristic times
1.06 Is
Is
0.1 Ib
“pick-up”
signal
time-delayed
output
Case of current sag.
1.06 Is
Is
0.1 Ib
“pick-up”
signal = 0
time-delayed
output = 0
Case of circuit breaker tripping.
0.1 Ib
15 ms
Operating time < 50 ms
Overshoot time < 35 ms
Reset time < 40 ms
(1) In reference conditions (IEC 60255-6).
0
&
T
0
time-delayed
output”
“pick-up”
signal
PCRED301005EN - 06/2008