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Simplified Low-cost Microprocessor Relay Protection Devices



Redundant CT circuits
bypass power source


Backup trip via CB
current solenoids


Digital oscilloscope
Event log


Integration in


Reliable operating under
heavy ambient conditions


RZL-03 device series used for relay protection of medium voltage feeder lines. RZL-03 device series grants excellent cost efficiency for solutions where trivial power engineering task complicates with heavy environment conditions. Devices are available for mounting dorectly on outdoor switchgear bays. Interference, overcurrent and overvoltage tolerant, water and dust resistant front and side panels IP54, vibrations and shock sistainable, wide operating temperature limits.

RZL-03 application range extends widely when coupled with one of RELSIS® simple electromechanical and electronic single-parameter solid relays of NL and EL Voltage relay series, AL Current relay series, PE Auxiliary relay series e.t.c.

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Device functions

  • Instantaneous single-stage current cutoff (CC) and two-stage delayed overcurrent (OC) protection;
  • CC and OC stage blocking option provedes logic sensitivity protection functions performance;
  • OC stage acceleration option may be used for Switch-On-to-Fault trip acceleration performance;
  • Additionally to OC stages definite time delay setting, second overcurrent stage can be assigned as one of typical time-current curve options available;
  • Circuit breaker auto-reclosing;
  • Circuit breaker control circuits supervision;
  • Redundant power supply feedeng from current transformer (CT) circuits, avoiding switch-on current inrush in CT secondary on transfer switching;
  • Self-supervision;
  • Real-time current and frequency values measurements display;
  • Non-volatile memory of the last trip fault current value.


  • Reliable operation under heavy environment conditions, interruptive supply auxiliaries, solid analog and binary input interference withstand;
  • Binary output and indication non-volatile locking on trip operation (until manual reset);
  • Small-size casing for flush or protruding mounting;
  • Water splash proof, vibration and shock sustainability, high interference and overcurrent tolerance, wide operating temperature limits;
  • Easy human-machine interface with 10-character single-line led display and 4 button keyboard;
  • RZL-03.7xx and RZL-03.8xx device modifications support MODBUS data transfer protocol via RS-485 interface connection including

Technical parameters

Power supply units parameters
Operating supply voltage range, DC or AC 90 - 254 V
Power-on availability time 0,2 s
Operating supply interruption 0,5 s
Device burden 10 Wt
Current inputs number 2
Current input parameters
Rated current 5A
Maximum continuous current (see wiring diagram) 1 - 8 A
Measurable current range 1,5 - 99,0 A
Current thermal withstand, 1 s (see wiring diagram) 10 (500) A
Data interface RS-485
Data protocol Modbus RTU
Connection speed 9600, 19200, 38400 kbps
Binary input parameters
Numbers of inputs 3 or 4
Rated AC, DC voltage 230 V
Maximum voltage, continuous 310 V
Binary output parameters
Number of binary outputs 4
Maximum DC voltage trip 300 V
Maximum AC voltage trip 400 V
Maximum DC LR-circuit trip current, time constant τ ≤ 20 ms 0,4 A
Mounting type Flush/Protude
Device dimensions (WxHxD) 180x135x140 mm
Operating ambient temperature range -40 to +55 °C
Maximum Humidity at 25 °C 98%
Insulation resistance, more than 50 MΩ
Insulation overvoltage withstand 5 / 2 kV
Instantaneous / continuous
Weight, less then
3 kg

Wiring Diagrams

RZL-03.100 - wiring

Connection diagram of RZL-03.100

RZL-03.200 - wiring

Connection diagram of RZL-03.200

RZL-03.104 - wiring

Connection diagram of RZL-03.104


RZL-03 - dimensions_1

RZL-03 - dimensions_2

RZL-03 - back

# Download the brochure. Protection and control devices.