The device tripping RCDs.

At present, the RCD is successfully installed in the newly reducible installations. But the installation and application of the RCD and to date raises questions as subscribers and the employees responsible for the installation of electrical installations.

So what is an RCD?

Devices (RCD), responsive to the differential current, along with overcurrent protection devices include additional types of human protection against indirect contact provided by auto power off.

In contrast to the protection against overcurrent RCD is the only human means of protection from electrocution at low current circuit, reducing isolation, not efficient enough. Protection against overcurrent (using protective vanishing) ensures human protection against indirect contact - by tripping circuit breakers or fuses the damaged section of a short-circuit on the case. Of all the electrical safety devices RCD it is the only one that protects a person from electric shock in direct touch to one of the live parts. Just RCD is an excellent protection against possible damage to the insulation, wiring and electrical faults are considered the main cause of fires and fires that occur in electrical installations.

A bit of history.

For the first time in 1937, the firm Schutzapparategesellschaft Paris & Co. It produced the first active device on the basis of the differential transformer and a polarized relay, which had sensitivity of 0.01 A and speed of 0.1 seconds. In the same year, with the help of volunteers - an employee of the company was carried out live-test of the RCD. In 1960-1970 gg. worldwide, primarily in Western Europe, Japan, the United States began the active introduction of the RCD in wide practice. Currently, hundreds of millions of RCD successful, as evidenced by the official statistics, to protect life and property of the citizens of France, Germany, Austria, Australia and other countries from electrocution and fires.

The principle of the RCD.

RCD - high-speed protection means responsive to the differential current in the conductors which pass electricity to the protected electrical installation. RCD action based on the differential transformer toka.Summarny magnetic flux in the core - F is proportional to the difference of the currents in the conductors, which are the primary windings of the current transformer, IL and IN, induces in the secondary winding of the transformer electromotive force under the action of which a secondary winding circuit current flows I proportional to the difference between the primary currents. This current and actuates the trigger. In normal operation the net magnetic flux is zero, the current in the secondary winding of the differential transformer is also zero. When you touch the person to open or conductive parts to the housing appliance, on which there was a breakdown of insulation, for phase conductor through the RCD in addition to the load current flows an additional current - leakage current, which is a current transformer differential (difference). Inequality currents in the primary windings causes unbalance of magnetic fluxes, and consequently, the occurrence of the secondary winding of the differential current transformed. If the current exceeds the setting threshold trigger the body element, the latter is activated and acts on the actuator. To control serviceability (serviceability) RCD test circuit is provided (the "Test" button) works by creating an artificial residual operating current.

Basic mistakes when installing the RCD.

The most common mistake when installing the RCD is a connection to the load of RCD in the circuit where there is a neutral conductor connection N with exposed conductive parts of electrical connection or with protective earth conductor PE. In this case, the probability of "arbitrary" RCD trip is very high. Also, the following error: The connection to the load neutral conductor to the RCD, the connection load neutral conductor to another RCD bridge between the zero workers of different conductors of the RCD, the connection on the load side conductors PE and N in the socket.

An example of switching the RCD.

Regulatory regulations.

  • Terms of electrical devices Ed. 7th.
  • GOST 12.4.155-85. "Circuit breakers. Classification. General requirements"
  • GOST 50807-95 (IEC 755-83). "Protective devices controlled differential (residual) current"
  • GOST R 50571.3-94 (IEC 364-4-41-92). "Electrical installations of buildings. Safety requirements. Protection against electric shock".
  • GOST R 50571.11-96 (IEC 364-7-701-84). "Electrical installations of buildings. Part 7: Requirements for special installations. Section 701. Bathrooms and shower rooms."
  • GOST R 50571.15-97 (IEC 364-5-52-93). Part 5: "Selection and installation of electrical equipment. Chapter 52. Wiring".
  • GOST 50 669-94. "Electricity and electrical mobile (inventory) buildings of metal or with metal frame for street trading and consumer services. Technical requirements."

And others …