HV/MV transformer digital protection relay
CZAZ-TH protection relay provides complex protection of HV side of power transformer. The relay is equipped with speciallised bay controller. Digital design of the relay ensures high level of accuracy, reliabilty and dependability. In order to provide full protection of power transformer, the external differential relay must be installed.

Manuals, diagrams, technical details


Product description

Protection set

51 definite-time overcurrent against external faults
51 overcurrent against overloads
51 inverse-time overcurrent against overloads and faults
50 overcurrent against internal faults
51N ground overcurrent
· arc flash detector (optionally)

Main features

  • bay controller with standard control operation mode implemented which ensures safe in both local and remote modes based on breakers position supervising

    Additional functions:

    – cooperation with UFLS and auto reclose after UFLS automation

    – cooperation with busbar protection systems

    – cooperation with CB failure protection

    Cooperation with breakers function ensures:

    – supervising of CB postition

    – SF6 gas pressure supervising (only CZAZ-TH v.3)

    – supervising of control switch (local – out-of-service – remote) (only CZAZ-TH3 v.3)

    – Trip Circuits Supervising functions and auxilliary voltage supervision

    – Open command and Close command

    – Disconnector and Earthing switch postion supervising

    – 8 programmable relay outputs

    – 6 binary inputs for cooperation with external protections, incl. 2 for cooperation with Bucholtz protection of transformer and transformer tap changer

    – 2 TRIP purposes relay outputs allowing to direct connection with CB coils and with Trip Circuit Supervision function

    – 7 measuring inputs (phase currents, phase-to-phase voltages, residual current/voltage)

    – Measuring of current electrical vaules (phase currents, zero-sequence current, phase-to-phase voltages, active power, reactive power, active energy counter, power factor)

    – Event and disturbances recorders

    – ab. 70 unique events register with capacity to memorise up to 500 events

    – disturbance recorder of sampling frequency 1000 Hz (7 analog signals and 16 binary signals)

    – parameters of last disturbance recorder: maximum current during disturbance and duration of disturbance

    – number of protection operations counter and sum of tripped current counter

    – optical visualisation of most important states of protected object (8 LED diodes)

    – autotest and autocontrol system

    – screw terminals for current inputs and pluggable screwless terminals for other circuits

    – autonomic communication by local Human Machine Interface

    – remote communication with PC computer or supervising system


Rated current In 1A or 5A
Rated voltage Un 100V
Rated frequency fn 50Hz
Auxilliary voltage Up  110V, 220V DC
Burden in analog inputs ≤0,5VA/input
Burden in auxilliary voltage supply ≤20W
Operating time ≤40ms
Continuously thermal withstand of current inputs 2,2In
1 sec thermal withstand of current inputs 80In
Dynamic withstand of current inputs 200In
Continuously voltage withstand of voltage inputs 1,2Un
10 sec voltage withstand of voltage inputs 1,5Un
Relay outputs data
Max. breaking capacity by 250V DC
– resistive load 0,3A
– inductive load of L/R ≤40ms 0,12A
Max. breaking capacity by 250V, 50Hz
– inductive load, cosϕ=0,4 3A
Continuous contact carry 5A
Ambient temperature (268÷313)K/(-5÷40)°C
Relative humidity ≤ 80%
Ingress Protectrion degree IP40
Dimensions (height x width x depth)
– surface mounting 223 x 337 x 260 mm
– flush mounting 288 x 145 x 305 mm
Electromagnetic compatibility according to EN 60255-26
Insulation according to EN-60255-5

Available versions of CZAZ-TH – depends on bay configuration:


Details – see product datasheet

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