Digital protection relay for MV power network
Medium Voltage protection relay type mZAZ PLUS is dedicated to be used in power system protection and control systems of MV network. mZAZ PLUS relay provides comprehensive protection and control  functions library. The device is equipped with settable analog inputs, it provides customizable set of protection functions, programmable logic, measurments, signalling and other functions – based on open software library, what allows to adapt relay to protected object and fullfil customer’s needs.

Manuals, diagrams, technical details


Product description

Protection and control functions list

50/51 Instantonous and definite-time overcurrent protection, three stages
51 Inverse time overcurrent protection
49M/R Thermal overload protection
46 Negative sequence overcurrent protection
67 Directional overcurrent protection
50N/51N Ground fault overcurrent protection, instantonous and definite-time – two stages
51N Ground fault overcurrent protection, inverse time characteristic
59N/67N Ground fault directional protection for MV, two-stage
59N/67N Ground fault directional protection for HV, two-stage
21N Ground fault, admittance-based protection
27/59 Under and overvoltage protection, three stages
27SA Undervoltage, rate of change of voltage
27I Undervoltage, integral protection
27D Undervoltage, positive component protection
47 Negative sequence overvoltage protection
59N Residual overvoltage protection
59S/27S Rate of change of voltage
V VS Voltage vector shift protection
37 Undercurrent, against motor idle
38 Temperature protection
48/66 Motor start-up supervision
51LR Overcurrent, against locked rotor
51LR Overcurrent, against motor stall
32R Reverse power protection
32S Rate of change of power protection
81H/81L Over- and underfrequency protection, five stages
81SA Rate of change of frequency protection
62 External protection
79 Automatic reclosing function
Under frequency load shedding
Under voltage load shedding

Main features

  • customizable by manufacturer set of protection and control functions
  • programmable logic set by manufacturer – setting is partially available for user
  • free SMiS software for setting the relay
  • 8 measuring inputs for use with protection purpose transformers
  • 2 measuring inputs for use with transducers: 4-20 mA, 0-10 V
  • 8 fully programmable relay outputs
  • 12 binary inputs divided into three sections
  • front panel equipped with alphanumeric display (2×16) and set of buttons
  • measurments of measured and calculated electrical values
  • real time clock
  • event recorder and last disturbance parameters recorder
  • recorder of samples or magnitudes of measured values during disturbance, logic inputs recorder
  • sum of tripped currents counter
  • counter of protection operations
  • trip command
  • RS-485 and mini-USB port for remote control by MODBUS-RTU protocol
  • self-test system to control proper operation of relay
  • screw terminals for measuring inputs, pluggable terminals for other inputs
  • multilevel security against unauthorised access
  • high stability, accuracy and reliabilty ensured by digital technology


Rated current In 1 A, 5A
Rated voltage Un 100/√3 V, 100 V, 230 V, 400 V
Rated frequency fn 50 Hz
Rated auxilliary voltage Up

24 V, 48/60 V DC

110 V, 220 V DC

110 V, 230 V AC

Control voltage Ups acc. to aux. volt. Up
Setting range of start values acc. to prod. datasheet
Accuracy of current input 1 %
Accuracy of voltage input 0,5 %
Accuracy of power measure 2,5 %
Accuracy of angle measure 1,5 º
Burden of analog inputs ≤ 0,5 VA /input
Burden of auxilliary voltage supply ≤ 8 W
Continuous thermal withstand of current inputs 4 In
1 sec thermal withstand of current inputs 80 In
Dynamic withstand of current inputs (10 ms) 200 In
Relay outpus S1-S5 data:
Continuous contact carry 6 A/250 VAC/24 VDC
Max. breaking capacity AC1 1500 VA/250 V
Max. breaking capacity DC1 192 W/24 V
Relay outpus S6-S8 data:
Continuous contact carry 8 A/250 VAC/24 VDC
Max. breaking capacity AC1 2000 VA/250 V
Max. breaking capacity DC1 192 W/24 V
Operating temperature range -20 …. 55 ºC
Relative humidity (with no condensation) ≤ 95%
Ingress Protection degree IP40
Weight approx. 1,2 kg
Dimensions (width x height x depth) 167 x 110 x 154 mm
Electromagnetic compatibility according to EN 60255-26
Insulation according to EN 60255-27

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