Functions andcharacteristics

A-12

60 250 400 500 60040

STR23SE 0SN

STR23SE / STR53UE

STR23SE / STR53UE

STR23SV / STR53SV??

Protection of distribution systemsSTR trip units for Compact NS400 to 630

Compact NS400 to 630 circuit breakers,types N, H and L, 3-pole and 4-pole, maybe equipped with any of the STR23SE,STR23SV, STR53UE and STR53SVelectronic trip units.The STR53UE and STR53SV trip unitsoffer a wider range of settings and theSTR53UE offers a number of optionalprotection, measurement andcommunications functions.

Protection of systems with anoverloaded neutral

Standard protection with selectivity

DB

1051

16

Protection of systems suppliedby generators.Protection of long cables

Selection of the trip unit depends on the type of distribution system protected andthe operational voltage of the circuit breaker.Protection for all types of circuits, from 60 to 630 A, is possible with only five trip-unit catalogue numbers, whatever the circuit-breaker operational voltage:b U y 525 V: STR23SE, STR23SE OSN or STR53UEb U > 525 V: STR23SV or STR53SV.Trip units do not have a predefined rating. The tripping threshold depends on thecircuit breaker rating and the LT (long time) current setting.For example, for an STR23SE trip unit set to the maximum value, the trippingthreshold is:v 250 A, when installed on a Compact NS400 250 Av 630 A, when installed on a Compact NS630.

STR23SE (U y 525 V) and STR23SV (U > 525 V)electronic trip units

ProtectionThe protection functions may be set using the adjustment dials.Overload protectionLong-time protection with an adjustable threshold and fixed tripping delay:b Io base setting (6-position dial from 0.5 to 1)b Ir fine adjustment (8-position dial from 0.8 to 1).Short-circuit protectionShort-time and instantaneous protection:b short-time protection with an adjustable pick-up and fixed tripping delayb instantaneous protection with fixed pick-up.Protection of the fourth poleOn four-pole circuit breakers, neutral protection is set using a three-position switchto 4P 3d (neutral unprotected), 4P 3d + N/2 (neutral protection at 0.5 In) or 4P 4d(neutral protection at In).

Protection of an overloaded neutral (OSN):For 4-pole circuit breakers, special protection of systems with high 3rd orderharmonic contents. In position 4P 4d, the switch sets the neutral protectionthreshold to 1.6 x Ir.

IndicationsA LED on the front indicates the percent load:b ON - load is > 90 % of Ir settingb flashing - load is > 105 % of Ir setting.

TestA mini test kit or a portable test kit may be connected to the test connector on thefront to check circuit-breaker operation after installing the trip unit or accessories.

t

Isd I0 Ir li

1

2

3

45

IsdIr

STR 23 SE

Ir

x Io

Io

-test

+

90105 %Iralarm

x In

6 1 37

.5

.63.7

.91

.8.85

.9.95

1

.88.93

.98

.8

234

5 678

10

Isd

x Ir

1 long-time threshold (overload protection) Ir2 long-time tripping delay3 short-time pick-up (short-circuit protection) Isd4 short-time tripping delay5 instantaneous pick-up (short-circuit protection) Ii6 test connector7 percent load indication

E24

094D

B10

3751

Protection of systems U > 525 V

550E2100_A4aA19.P65 06/11/2007, 09:4012