Download - Power Logic

Phase Undercurrent
ANSI Code 37
Operation
Block Diagram
This single-phase protection:
b Picks up when phase 1 current drops below the
Is set point
b Is inactive when the current is less than 10% of IB
b Is insensitive to current drops (breaking) from circuit
breaker tripping
b Includes a definite time delay (T)
MT10426
T
0 0.1 IB
Is
I
Operating Principle
MT10865
Ia
I < Is
15 ms 0
T
0
Time-Delayed
Output”
“Pick-Up”
Signal
I>
0.1 IB
Characteristics
t
3
DE50367
Protection Functions
Is Set Point
Setting
Accuracy (1)
Pick-Up/Drop-Out Ratio
Time Delay (T)
Setting
Accuracy (1)
Resolution
Characteristic Times
Operating Time
Overshoot Time
Reset Time
(1) In reference conditions (IEC 60255-6).
1.06 Is
Is
0.1 IB
15% IB y Is y 100% IB by steps of 1%
±5%
106% ±5% for Is > 0.1 IN
50 ms y T y 300 s
±2% or ±25 ms
10 ms or 1 Digit
< 50 ms
< 35 ms
< 40 ms
“Pick-Up”
Signal
Time-Delayed
Output
MT10866
Case of current sag
1.06 Is
Is
0.1 IB
“Pick-Up”
Signal = 0
<15 ms
Time-Delayed
Output = 0
Case of circuit breaker tripping
32
63230-216-208C1
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