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The first only effective when the release powered (it also records
overloads that have not lasted long enough trip the release), while the second works even when the release not powered, reducing any trip
times the case immediate reclosing and enabled soon the tripped.9.9.
12.1 Protection “L”
The "L" the only protection that cannot disabled because for self-protection against overloading the relay itself.2.1.2.3 Zone selectivity “S”
The zone selectivity function, guaranteed only auxiliary voltage provided, enables the area the fault isolated, only isolating the part
of plant nearest the fault, while keeping the rest the plant operational.9.
The protection trip time inverse time given the expression:
for <12In and for >12In where the fault current and I1the protection threshold and with t1/ (ln 9/8)
NB: Time expressed seconds. The other characteristics are the same those for thermal memory
"L" (see par.
Programmed time ts
• Start-up time
The start-up time common all the protections involved.1 Thermal memory “S”
The thermal memory function can enabled for cable protection the case where the curve with inverse time selected. The types trip curves
settable are divided into two groups according the IEC standard 60255-8.
32/1 08
.2.9.2. new start-up possible
after the current has dropped below this threshold.01s.
This done connecting all the zone selectivity outputs the releases belonging the same zone one another (ZSO=K51/SZout) and taking
this signal the zone selectivity input (ZSI K51/SZin) the next release the supply side. The latter
must intended follows:
- Passage the RMS value the maximum current over one single adjustable threshold (0.1.2..
The start-up function enables the protection threshold and changed during time interval lasting "ts", starting from "start-up".
The function can disabled and setting characteristic the single protection units.10In, 0.
12.12.2.
12. This based the
"tS" parameter defined the trip time the curve (t2) selected 1.
The PR122/DC fitted with two instruments make this thermal memory.2.5x12.
12.2. Range: 0..1).
Model 3447 pparatus Emax cale
Doc.1. 30s, with steps 0.
T In
(■»)for and for /n
where calculated the basis the evolution the current providing there overload condition.2.1s .1In steps)..
It the PR122/DC release that automatically decides which the two use, according the various situations.2.9.1 Thermal memory “L”
The thermal memory can enabled protect the cables the basis the "hot state" tripping curve IEC 60255-8.2. the wiring has been done correctly, all the zone
selectivity inputs the last circuit-breakers the chain and all the outputs the circuit-breakers the head each chain must empty..
NB: Time expressed seconds.9.
12. 1SDH000635R0002
Page No.2 Start-up threshold “S”
The start-up function can selected the case where the curve with fixed time selected.2 Protection “S”
This protection can disabled; can the fixed time (t=k) inverse time (t= k/i2); the latter case, the trip time given the expression:
m ax
1 -12
(I,)2
- where where the fault current and the protection threshold.9 Description the protection functions
12.9. 12. No
