Digital protection unit dedicated for large power generators and power units
CZAZ-GT is a protection set providing complex protection of generator-transformer unit of every generation power against every type of fault or improper working conditions. CZAZ-GT protection is designed in digital technology, it provides both general and specialised protection functions, it generates trip signals and alarms, it measures custom electrical values, recording of analog and binary signals and it communicates with control system. CZAZ-GT unit is freely programmable, which allows to adapt the protection set to different system configuration but also it allows to easily adjust the principle of operation depending on previous experience. The typical construction is a two-cabinet system, suplied by independent voltage sources, which allows to achieve the redundancy of protection and measuring circuits.

Manuals, diagrams, technical details


Product description

Protection set

Protection functions are programmed during configuration. The device is programmed by using so called protection library. Protection functions are energized by electrical values obtained by digital filtration of analog signals received from protection transformers.

A typical CZAZ-GT protection set consists of the set of functions listed below:


87G Generator differential
87B Power unit differential
87T Transformer differential
51G Overload/overcurrent protection of generator stator
51Z Against phase-to-phase generator faulst
21 Admittance-based power unit protection
32 Reverse power protection
67 Directional, against loss of load
59 Overvoltage of power unit
40/27 Loss of excitation
81 Over-/underfrequency
24 Transformer overexcitation volt per hertz protection
46 Negative sequence definite-time overcurrent protection
46inv Negative sequence inverse time overcurrent protection
78 Slipping pole protection
59GN Generator residual voltage protection
64S 100% of generator stator protection, 3rd harmonic based
51N Ground overcurrent protection of power unit
51ET Overload protection of excitation transformer
51TT Overload protection of step-up transformer
64R Earth fault protection of generator rotor
49R Rotor thermal overload protection
50/27 Against connection of unexcitated generator

Protection functions are supported by logic circuits, which are designed using available measuring functions, Boolean operators and timers. It allows to configure advanced automation circuits, for example:

  • breaker failure logic, which provides redundancy trip signal of electrical part of power unit in case of failure operation of generator breaker
  • control generator excitation system, used in case of occurance of disturbances requiring immediate generator excitation system switch of

Main features

  • Number of binary inputs and relay outputs adjusted to the needs of protected unit (up to 320 in or out signals)
  • Number and type of analog inputs adjusted to the set of measuring transformers used at particular power unit (up to 50 inputs for each cabinet)
  • Possibility to adapt easily protection functions characteristics with biult-in software, designing logical circuits, timers and control algorithms, registers and signalling. The configuration of protection unit is carried out by the manufacturer or authorised representative
  • Great flexibility to configure sophisticated protection functions and logic system with possibility to upgrade according to the needs of the customer
  • Possibility to group signals in any configuration in order to get logical sum of trip signals
  • Trip outputs allowing direct control of unit breakers
  • Trip circuit supervision function
  • Measuring of electrical values (current, voltage, active and reactive power, frequency, phase shift, resistance, reactance, apparent impedance)
  • Event recorder (256 unique events, capacity up to 5000 events, time resolution 1 ms)
  • Disturbance recorder:
    • sampling frequency 1800 Hz
    • recording up to 40 analog signals and up to 128 binary signals
    • duration of recorder waveform – up to 500 sec. for one signal (approx. 10 sec. for 40 analog signals and 128 binary signals)
    • memory allows to save up to 32 files of registered disturbances
    • recording of sampled or digital filtered values (e.g. differential currents)
  • Optical signalling at HMI (14 LED diodes)
    • auxilliary voltage signalling
    • proper work of unit signalling
    • 12 programmable diodes for signalling other statuses
  • expanded self-control system and failure signalling
  • two power supply units per each cabinet providing full redundancy
  • autonomic communication with local HMI
  • remote communication with PC computer or SCADA system (two RS485 ports and one RS232 in front panel)
  • free PC software for Windows operating system


Rated current In 1A, 5A
Rated voltage Un 100V
Rated frequency 50Hz
Rated auxilliary voltage Up 110V lub 220V DC
230V AC
Burden of current inputs ≤1VA/input
Burden of voltage inputs ≤0,2VA/input
Continuous thermal withstand of current inputs 2,2In
Continuous thermal withstand of voltage inputs 2Un
1 sec thermal withstand of current inputs 80In
Dynamic withstand of current inputs (10 ms) 125In
Relay outputs data:
Control outputs:
Breaking capacity (DC or AC/50Hz) 5A
Continuous contact carry 5A
Signalling purposes outputs:
Max. breaking capacity – resistive load 0,3A
Max. breaking capacity – L/R ≤ 40 ms 0,12A
Continuous contact carry 3A
Operating temperature range (268÷313)K/(-5÷40)°C
Relative humidity (with no condensation) ≤80%
Ingress Protection degree IP40
Weight (1 cabinet) ~250kg
Dimensions – (height x width x depth) 2100 x 800 x 800 mm
Electromagnetic compatibility according to EN 50263
Insulation according to EN 60255-5

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