Overcurrent backup protection relay
Three-phase overcurrent relay eqiupped with energy store capacitors allows to trip the breaker in case of loss of auxilliary voltage. The relay is powered by short-circuit current and provides back-up protection for transformers, busbars and feeders.

Manuals, diagrams, technical details


Product description

Protection set

51 definite-time overcurrent protection

Main features

  • Designed to operate in three phase network as backup protection. It is supplied from all three phases with the ability to proper operation in case of one-phase fault
  • Equipped with a set of capacitors, which allows to store energy for trip purposes in case of lack of substation auxilliary voltage
  • For proper operation, the relay needs to be powered by current transformer secondary winding of rated power minimum value 25 VA
  • Auxilliary voltage is also required to ensure cyclic re-charge of capacitors
  • Optical indication (with LED diode) of auxilliary voltage presence
  • Binary input enabling carrying out routine test of relay
  • Relay contacts for signalling purposes (pick-up signal – 1 x NO and trip signal – 1 x NO) and two outputs to connect with trip coils with galvanic separation preventing from unwanted connection of capacitors with trip coils
  • Enclosure enables surface mount or install in 19” rack in control cabinet

Overcurrent backup protection ODR-2WA is supplied by current transformer of secondary winding rated power of at least 25 VA. If controlled current exceeds the set value, the process of storing energy in capacitors starts. At the moment when capacitors voltage reach the required value (approx. 300 V for 220 V aux. volt. version or approx. 150 V for 110 V aux. volt. ver.) the relay starts its operation. The capacitors are galvanicly separeted and after set time-delay connected to CB trip coils.

Proper operation of relay is auxilliary voltage independent. That ensures tripping of faulted object even in case of lack of auxilliary voltage when primary protections fails to operate.


Rated current In 1 A, 5 A
Rated frequency fn 50 Hz
Nominal auxilliary voltage Up 110 V, 220 V DC
Setting range of threshold current

0,5 A, 0,6 A, 0,8 A, 1 A, 1,3 A, 1,6 A for In=1A

2,5 A, 3 A, 4 A, 5 A, 6,5 A, 8 A for In=5A

Accuracy of current input 10 %
Supports Circuit-Breakers of following specification
  • trip coil rated voltage
110 V DC or 220 V DC
  • trip coil burden
≤ 600 W
  • coil resistance
≥ 80 Ω
Setting range of timer 3 – 8 s for I > 1,3 Ir
Burden of analog inputs ≤ 25 VA /input
Burden of auxilliary voltage supply ≤ 3 W
Continously thermal withstand of current input 2,2 In
1 sec thermal withstand of current input 80 In
Dynamic withstand of current input 200 In
Trip outputs data
Continuous contact carry 8 A
Max. breaking capacity – resistive load 0,3 A
Max. breaking capacity – L/R ≤ 40 ms 0,12 A
Max. breaking capacity – for AC 250 V, 50 Hz 3 A
Operating temperature range -25 …. 55 ºC
Relative humidity (with no condensation) ≤ 80%
Ingress Protection degree IP40
Weight 10 kg
Dimensions (width x height x depth) 300 x 200 x 135 mm
Electromagnetic compatibility according to EN 50263
Insulation according to EN 60255-5


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