Page 57 - Sace Emax 2 Catalogue

PROTECTION TRIP UNITS 3/33

t

I7

t7
I

t steady
state start-up
t

I7
I
t7 03
I Neutral protection: available at 50%, 100% or 200% of the phase currents, or disabled, it is applied to
t 50% 150%
100% 200%
L the overcurrent protections L, S and I.
t steady
S
state start-up
I
I

I
t Instantaneous Earth Fault (G-ANSI 50N): with trip curve without instantaneous delay.
t
t 100% 200%
I4 150%
50%
I4 L
t4
S
I I
I
t I
I3 Earth fault on toroid (G ext - ANSI 51G & 50GTD): with trip time independent of the current (t = k) or with
t
constant specific let-through energy (t = k/l ). Pre-alarm that 90% threshold has been reached permits
2
the fault to be reported to supervision systems without interruption of continuity. The protection uses
I4
t4 I the external toroid installed, for example, on the star centre of the transformer, and is an alternative to
the G and Rc functions. The function is active with an auxiliary supply.
t I

t
I2
t t2 Modified Differential Ground Fault (MDGF): Available with the trip time independent of the current
I3 (t = k) or constant specific let-through energy (t = k/l ). This protection function is designed for systems
2
I7 I with solidly grounded multi-source ground fault schemes (refer to instruction manual 1SDH001330R005).
The complete equipment level solution includes third-party phase current transformers, summing cur-
t7 I rent transformers, and a dedicated terminal (please refer to 1SDA114800R1 or 1SDA114798R1).
t
I1 I
t t1
Start-up function: enables protections S, I and G to operate with higher trip thresholds during the
t steady
state start-up starting phase, avoiding untimely trips due to high inrush currents of certain loads (motors, transform-
I2
t2 I ers, lamps). The starting phase lasts 100 ms to 30 s and is recognized automatically by the trip unit:
• at the closing of the circuit breaker with a self-supplied trip unit;
I • when the peak value of the maximum current exceeds the set threshold (0.1…10 x In) with an externally
I supplied trip unit; a new start-up is possible after the current falls below the threshold.
t
I1
t 50% 150% t1
100% 200%
L
t S Current unbalance (IU – ANSI 46): with constant trip time (t = k), protects from an unbalance between
the currents of the single phases protected by the circuit breaker.
I7 I I
I
t7
I
t

t steady
I4 state start-up
t4
I

t I

I3
t 50% 150%
100% 200%
L
S
I
I
t I

t I2
t2
I4 I
t4

t I
I1
t t1
I3
I

I

t

I2
t2
I

t
I1
t1

I