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The PR121/P unit can provide earth fault protection, achieved inside the relay vectorially adding together the phase and neutral currents.
Model 2234 Apparatus Scale
L 2778
Doc No- 2
Page No. The
fault current defined the following formula:
I n
If the circuit reveals faults, the module the sum these currents always nil; vice versa, the value the fault current takes larger and
larger value depending the entity the fault.
1 tio I"
This protection can disabled; the fixed time (t=k) type, and designed for nil intentional delay.1.5xI2.4 Protection "G"
This protection can disabled; can the fixed time (t=k) inverse time (t= k/i2) type; the latter case, the trip time given the expression:
* t,
where l/l4
If the fault current and I4the protection threshold, established the user.
When the protection tripped, the circuit-breaker opened the opening solenoid (TC).
PR121/P equipped with two instruments make this thermal memory.6.5 Protection against instantaneous sho rt-circuit "linst"
This function has single fixed-time protection curve.2 Protection "S"
This protection can disabled; can the fixed time (t=k) inverse time (t=k/I2) type; the latter case, the trip time given the expression:
100-1,
(I,)2
If the fault current and I2the protection threshold, established the user.6. 12.
33/158
.25x11.2. based the parameter defined trip time the curve (t1) selected
@1.
NB: Time expressed seconds.2.1.1 Thermal ory "L"
The thermal memory function can enabled protect the cables.6.12.
12. The other characteristics are the same those for thermal memory "L" (see par.1 Protection "L"
The "L" the only protection that cannot disabled because for self-protection against overloading the relay itself.2.
The trip time the release surely 100% the time selected after time has elapsed from the last overload last trip, else trip time will
be reduced depending the overload and time elapsed.2.
The type curve that can set /I2. The first one only effective when the release powered (it also records
overloads that have not lasted long enough trip the release); the second operates even when the release not powered, reducing any trip
times when closes again straight after and enabled soon the circuit-breaker tripped. This function can enabled through PR010/T, SD-Testbus2 SD-Pocket.
12.6.2.6.
The PR121/P release determines which one use according the situation.
12.2.
NB: Time expressed seconds.6Description the protection functions
12.
NB: Time expressed seconds. This based the "tS" parameter
defined the trip time the curve (t2) selected 1.
where \max
1 "
The thermal memory function can enabled for cable protection when the curve with inverse time selected.2.
The inverse-time protection trip time given the expression:
9 t
max
(I, /I,)2
1 where 12ln, where 12ln
If the fault current and I1the protection threshold, established the user.
max
12.6.1)
