Page 75 - SACE Tmax XT - Catalogue

PROTECTION TRIP UNITS 3/41

03
In step mode (controlled mode) the protection is tripped at a set threshold (I20) if the voltage is above
K
U, whereas it is tripped at the lower threshold of the factor Ks (I20 * Ks) if the voltage is below U.
1
Ks

V
UIU
K t In linear mode (restrained mode) two voltage limits are selected within which the protection is tripped
Extremely Inverse
t Extremely Inverse at the set threshold (I20) reduced by a factor of K corresponding to the measured voltage. The variation
Very Inverse
Standard Inverse
1 Very Inverse
8
Standard Inverse of the factor K is proportional to the voltage, and for voltages greater than the upper threshold (Uh) the
8eshold I20 works, whereas for voltages below the lower threshold (UI) the minimum threshold (I20 *
thr
Ks
Ks) applies.
V I
UI Uh
I
t S2(V) – 2nd protection against voltage-controlled overcurrent protection (ANSI 51V)
t Available in addition to the protection S(V), this enables total selectivity to be achieved in all installations.
It is possible to set the operating mode to: active, alarm only, or deactivated. The protection also ope-
U8 UV
U8 rates with the circuit-breaker open, thus allowing fault identification before circuit-breaker closing.
UV
t8
t8 V
V
t 2 Residual overvoltage (ANSI 59N)
t With a constant trip time (t = k), this protects against insulation loss in systems with insulated neutral
V23 V12 or with neutral earthed with impedance. It is possible to set the operating mode to: active, alarm only,
U9
OV
α α U9 or deactivated. The protection also operates with the circuit-breaker open, thus allowing fault
OV
3 V31 t8 t9 1 identification before circuit-breaker closing.
t8 t9 V
V
UF Underfrequency (ANSI 81L)
t
t With a constant trip time (t = k), this trips when the network frequency falls below a set threshold.
f12
UF
f12 UF
t12
t12
t12 f
t12
f
t OF Overfrequency (ANSI 81H)
t
With a constant trip time (t = k), this trips when network frequency exceeds a set threshold.
f13 OF
f13 OF
t13
t13 f
f
UF2 & OF2 Second protection against underfrequency and overfrequency (ANSI 81L and 87H)
t mean
f17 mean This enables two minimum and maximum frequency thresholds to be set simultaneously. For example,
voltage unbalance
U14 just an alarm can be set for tripping when the first threshold is reached, and the circuit-breaker can be
voltage unbalance
f12 t17 U14 set to be opened when the second threshold is reached.
U1 t12 U2 U3
U1 U2 U3 f
V1
V1
senso ciclico
senso ciclico

V3 V2
V3 V2