What is OUZO?

Hello, dear readers! Today it is necessary to continue the conversation on devices of protection of home lines, on such device as OUZO. Much of you know, and many, maybe, learn for the first time that OUZO is , perhaps, the only active way accepted around the world to secure people at accidental touch to current carrying parts and the equipment, against earth fault currents (leakage currents).


Externally OUZO it is very similar to the normal automatic machine.

This adaptation which will be able to carry out protection against the ignitions and the fires which arose owing to insulation failures or malfunctions of the electrical wiring.

History of creation of OUZO

Схема, поясняющая принцип защиты.

The scheme explaining the principle of protection.

The first OUZO was patented by the German firm RWE in 1928 when the principle of current differential protection which was earlier applied to protection of generators, lines and transformers was applied to protection of the person against defeat by electric current.

In 1937 Schutzapparategesellschaft Paris & Co manufactured the first operating device on the basis of the differential transformer and the polarized relay which had sensitivity 0,01 A and high-speed performance of 0,1 pages.
In the mid-fifties in Austria, Germany and in France mass implementation of OUZO in one and all electric units began. The copy of the photo of one of the first serial the OUZO produced in 1956 is given below.

There were years. Development of technology did not stand still. Gradually OUZO turned into the compact obligatory device.

Международная классификация УЗО

International classification of OUZO.

On the appearance OUZO bears to the normal automatic machine a strong resemblance: same body and lever of shutdown. As a matter of fact, OUZO can also act as AV that is as the switch of the certain site of the chain.

Presently demand for OUZO remains steadily big therefore along with domestic manufacturers, many foreign firms continue to release in significant amounts these devices in the most different modifications, is constant them improving.

There is a wish to tell about one feature. The term OUZO accepted in domestic special literature most precisely defines assignment of the device and its difference from other switching electrodevices. Now the international classification of OUZO developed by the international electrotechnical commission – MEK (IEC) works. That table of the international classification is included below.

Besides, the general name – RCD (residual current protective device) is accepted. If precisely to translate this phrase, then it will look so – the protection device on spill (differential) current.

Functionally OUZO can be defined as the instantaneous protective circuit breaker reacting to differential current in the conductors bringing the electric power to the protected electric unit. The block diagram of OUZO is included below.

The UZO major functional block is the differential transformer of current.

In absolute majority of OUZO which are made and operated now as the sensor of differential current the current transformer is used.

Структурная схема УЗО.

Block diagram of OUZO.

The starting body (or as it is called still, the threshold element) is usually carried out on sensitive magnetoelectric relays of direct action or electronic components.

There is its schematical drawing:

  1. Magnetic conductor.
  2. Winding.
  3. Permanent magnet.
  4. Anchor.
  5. Spring.
  6. Rod.

The operating mechanism includes the power contact unit with the drive mechanism.
To OUZO it is intended for continuous and long work.

It has to disconnect the protected network site at emergence in it the sinusoidal variable or pulsing direct current of leak equal to the disconnecting differential current of the device.

Схематический рисунок принципа работы УЗО.

Schematic drawing of the principle of work of OUZO.

OUZO, functionally not depending on supply voltage, should not work at removal and repeated inclusion of mains voltage. Automatic repeated inclusion should not produce OUZO.

OUZO also should not depend on availability of tension in controlled network. It keeps the working capacity at break of the zero or phase wire. Also OUZO has to work when pressing of the TEST button by you.

OUZO is protected from KZ currents by the consecutive protection device (here it is meant that it will be AV).

At the same time the rated current of ROM should not exceed the OUZO rated working current. It is possible to provide the table which can be useful further to you.

Номинальные токи ПЗУ.

Rated currents of ROM.

After everything told it is necessary to explain the principle of effect of OUZO.

Operating modes of the device

Схема работы УЗО с заземлением.

Scheme of work of OUZO with grounding.

As you see from this drawing, all process of work of OUZO can be broken into three modes:
The 1st mode – normal work.
The 2nd mode – activation in case of the problem of the magnetic flux.
The 3rd mode – the mode of operation and interruption in supply of tension.

Under the terms of functioning, are separated by OUZO into the types:
EXPERT – OUZO, reacting to the alternating sinusoidal differential current arising suddenly or slowly increasing.
And – OUZO, reacting to the alternating sinusoidal differential current and the pulsing direct differential current which are arising suddenly or slowly increasing.
In – OUZO, reacting to the variable, constant and straightened differential currents.
S – OUZO the selection (with endurance of time of shutdown).
 G – the same, as type S, but with smaller endurance of time.

Designs of OUZO of different producers can differ not only the parameters, but also schemes with connections.

The most widespread schemes of connection of OUZO

Схемы подключения УЗО.

Schemes of connection of OUZO.

According to the specifications there are two OUZO types.

Electromechanical – functionally do not depend on supply voltage. The power source, necessary for functioning, performance of protective functions, including shutdown operation, the signal – differential current to which it reacts is for the device of this look.

Electronic – functionally depend on supply voltage. Their mechanism for performance of operation of shutdown needs the energy received or from controlled network, or from the external source. But use of such devices is more limited owing to their smaller reliability, exposure to influence of external factors.

So, having read this publication, you decided to install this device. But you do not hurry. All electricians – both experienced, and beginners, – can make mistakes at connection. And, that it did not occur, it is necessary to take data from the number of schemes where the most typical mistakes are specified into account.

Типичные ошибки при подключении УЗО.

Typical mistakes at connection of OUZO.

In conclusion it is necessary to add that on each OUZO there has to be the permanent marking with the indication of such data as:

  1. Name or trademark (brand) of the manufacturer.
  2. Designation of type, number according to the catalog or numbers of the series.
  3. Rated voltage of U.
  4. Rated frequency if by OUZO it is developed for the frequency other than 50 or 60 Hz.
  5. Rated current of load of I.
  6. The rated disconnecting differential current of ID.
  7. The rated greatest including and disconnecting switching ability of Im.
  8. Rated conditional short-circuit current of IZ.
  9. Degree of protection (only in case of its difference from IP20).
  10. Symbol (S) for (S G) devices – for devices of G type.
  11. The instruction that OUZO functionally depends on mains voltage if it takes place.
  12. Designation of governing body of the control device – the TEST buttons.
  13. Scheme of connection.

Your right choice of OUZO depends on this marking.

Degree of protection of OUZO in standard conditions of operation after completion of mounting has to correspond to the class IP 20.
Also to yours several tables which will be interesting to you are presented.

Пределы превышения температуры частей УЗО

Limits of exceeding of temperature of parts of OUZO.

Нормы VDE для различных объектов

Norma VDE for different objects. 

  1. Sergey

    Good evening! Received, understood. Class!

    To answer
    • Andrey

      Sergey we are glad that could help you.

      To answer
  2. Yury

    Hello! I would also like to ask the question: where it is correct to put the circuit breaker — to ouzo, or later?

    To answer
    • Andrey

      The AV installation on protection of the line is established after OUZO.

      To answer
    • Andrey

      Yury if not difficult send you the e-mail address on which we can send you materials on the question interesting you (only the earnest request the address has to be true).

      To answer
  3. Sergey

    Good evening! I would like to ask you several questions: how does OUZO what automatic machine of protection is put before it whether it is possible to integrate the wires leaving OUZO work? Thanks in advance.

    To answer
    • Andrey

      Sergey sent you materials on the questions interesting you.

      To answer
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