The Differential-Protection Relais replaces the DSW-1 and DSW-2 types. It is function-compatibel to these older types.

The DSW- 4 is a 3-phase Differential Protection Relay. Input currents from two measuring points e.g. generator starpoint and C.T.'s inside switchgear are compared to each other.

The protected area is between the 2 games of current transformei's. Earth leakage currents within the protected area and within the adjusted setting cause trip of relay. Faults out of the protected area du not cause a trip signal.

To obtain safe function of the relay and to avoid unexpected trips the characteristic of 1he 6 C. T .'s used should be considered to be same.

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The setting range is 5 to 20 % of the nominal current. For each of the 3 phases the trip range may be selected seperately by potentiometers tocated on the relay front.

Characteristic and accuracy of the C.T.'s may limit the settable sensivity of the relay. C.T,'s ordered out of same producion series with same characteristic and same burden and accuracy will enable to make settings down to 5 %.

Correct wiring concerning current direction and C.T. pairs should be checked before commissioning as this is an essential precondition tor correct functlon.

The relay is factory preset to same values of the C. T. games. If necessary an adjustment can be made after removal of front plate by built-in potentiometers. If changes of Ihe factory pre-setting has been made the functon of the relay has to be retested within Ihe complete measuring range.

A jumper inside the relay enables to select Ihe start-up inhibit of the relay for either 0,5 sec. or 5 sec.

The relay has 4 potential-free relay-change-over contacts. If the differential current exceeds the presetted value both contacts R1/R2 are de-energised and both contacts A1/A2 wil become energized.
The green LED ‘R’ will light up if the contacts R1/R2 are energized. The red LED will be light up if the contacts A1/A2 are energized.

If the red LED is lightning permanently after start of operation it is necessary to check the correct wiring of the relay. Because of the metering principle of the device the correct connection of the terminals ‘k’ and ‘l’ is essential in each phase.
If the foult is foundet in the accuracy of the C.T.’s it may be required to adjust the C.T.’s symmetry by the internal symmetry-potentiometer.


Kunststoff Makrolon 8020 Light Gray
nach VDE 0100 und VBG 4


Rail 35 mm DIN EN 50022
alternative Screw-mounting


L 75 x B 99,7 x H 110 (mm3)


Enclosure IP 40
Terminals IP 20

device cover

clear-transparent, lead-sealable


-10... + 50 Grad C

Aux- voltage

12 / 24 V DC


max. 2 W


6 x 0...10 A AC ( 20 A , 10 sec )


5..20 %,
Settable seperately for each phase


0,5 / 5 sec.
setable by internal jumper


30 ms


2 Relais-change-over contacts, no Signal current.
2 Relais-change-over contacts, working current

Max. Load 250 V AC, 125 W


12/24 V


Technical data may be changed without notice.

Datum: 25.09.2019  vorherige Version: 22.09.2019 Start: 07.1997    Auflage 2