MV/LV transformer protection relay
mZAZ-T is protection relay dedicated to protect MV/LV transformers. The device integrates protection functions as well as control functions, measuring and recorders. mZAZ-T can be applied in MV and LV systems.

Manuals, diagrams, technical details


Product description

Protection set

50/51 instantenoues/definite-time, three-stages, three-phase overcurrent protection
49R thermal overload, inverse-time current protection
46 current unbalance protection
67N directional ground overcurrent protection
59N residual overvoltage protection
50N/51N ground overcurrent, definite-time, two-stages protection
51N ground overcurrent, inverse-time protection
62 external protection

Main features

  • 4 measuring inputs (IL1, IL2, IL3, U0)
  • Cooperation with built-on transformer protection devices
  • 4 setting banks
  • measurment of analog input values
  • real time clock
  • event recorder with capacity up to 500 records
  • last disturbance parameters recorder
  • samples or magnitudes of disturbance and logic states recorder
  • Tripped currents counter
  • Two binary inputs for cooperation with external protection purposes, possibility to be used as blocking inputs
  • Trip impulse
  • alphanumeric LCD display (2×16) and six buttons enabling operation of the relay
  • visual indication (by LED diodes) of pick-ups and trips, exceeding of counters or proper operation of relay
  • 7 programmable relay outputs (S1-S7)
  • RS-485 port for communication with PC computer or supervision and control system (MODBUS-RTU protocol)
  • self-test system of proper operation of relay control
  • enclosure construction enables three types of mounting: 35 mm rail, surface mount or flush mount

Communication interface provides measured and calculated electrical values, binary inputs and outputs states and saved records. The manufacturer provides PC software allowing to set the relay, confirm signals, graphical display of measured values and browse records.


Rated measuring current 5A
Rated measuring voltage 100V
Rated frequency 50Hz
Auxilliary voltage 24V DC, 48V – 60V DC,
110V DC/AC, 230V DC/AC
Control voltage acc. to aux voltage
Setting range of threshold value of voltage in 59N protection (0,05÷1,20)Uon
Setting range of current threshold values
(0,2÷30)In for „50/51” def. time
(5÷500)mA or (50÷5000)mA for „50N/51N” def. time
(5÷100)mA or (50÷1000)mA for „50N/51N” inv. time
(0,5÷1,5)Ib for „49R” protection
(0,1÷1)In for „46” protection
Base current Ib setting range (0,1÷2,5)In
Setting range of 67N protection function
– current threshold value (5÷100)mA or (0,05÷1,00)A
– voltage threshold value (0,01÷0,99)Uon
– characretistic angle (0÷90)° – cap.
Setting range of sum of tripped currents counter (1÷ 65000)In
Setting range of operating time
– definite-time operating characteristics (0÷99,9)s
– according to 49R protection function characteristic
Relay response time for 50/51 protection functions ≤40ms
Relay response time for ground protection functions ≤100ms
Accuracy of voltage inputs 0,5% if Uo=Uon
Accuracy of current inputs 1% if I=In
Accuracy of time measuring 1% ± 10ms
Burden in measuring inputs ≤0,5VA/input
Burden of supply module ≤6W
Thermal/dynamic withstand of current inputs 80In /250In
Continuous/thermal withstand of voltage inputs 1,2 Uon/1,44 Uon
Relay outputs data:
Max. breaking capacity by 250V DC
– resistive load 0,3A
– inductive load of L/R ≤40ms 0,1A
Max. breaking capacity by 250V, 50Hz
– inductive load, cosϕ=0,4 3A
Continuous contact carry 6A
Ambient temperature (253÷328)K/(-20÷55)°C
Relative humidity ≤80%
Ingress Protection degree IP40
Weight ~0,8kg
Dimensions (height x width x depth) 75 x 100 x 120 mm
Electromagnetic compatibility according to PN-EN 60255-26
Insulation according to PN-EN 60255-5

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